I would think that it would work using pressure plates and laser sensors, the crew wouldn't die because the need to avoid the deck plate twelve to the left of the statue in corridor 44G is as ingrained in them as the fact that it is corridor 44G. Anyone who sets off a trap is a "Nuwmin", anyone who survives setting off a trap is a "bastard Nuwmin sir" and immediately promoted.

I'm not trying to throw a monkey wrench in this parade, but let me be frank.  I've never attempted to do deck layouts and the ones I've seen are, IMO, deficient.  A capital ship 3 miles long x 1 mile tall x 1 mile wide is going to have over a thousand miles of corridors if the corridors are all spaced 100 yards apart and the decks are all 300' tall.  I find it likely that a capital ship has more like 10,000 miles of main corridors, 30,000 miles of secondary corridors, and untold mileage of access passages and crawlspaces.  The sheer immensity of these ships' interiors is almost inconceivable.  Ever seen a real aircraft carrier?  You could fit about 400 of those in a main cargo hold of one of these capital ships.  Those antennae that stick out of the artwork you see aren't antennae at all.  Those are towers that are larger than our own world's largest skyscrapers by degrees.  That is, to me, why boarding actions are even possible in the first place.  It's just not that hard to find a remote place along the hull that isn't covered by the small gun turrets, burn a hole through the hull, set some explosive charges, and whisk away.  The actual damage done is probably minimal, but the immediate damage probably intereferes with the ship's combat abilities.
 
These ships are difficult to navigate on a good day with a perfect map, which probably doesn't exist.  A tenebro maze is an improved version, which is a real nightmare to an invader.

Quite a Mary Sue...
 
I'm afraid that with so much power they would not roleplay at all. There is no one who could punish them so they will do whatever they want. Kill, maim, burn and so forth.

Hostile Acquisition and Book of Judgement would be mandatory for a campaign in Askelon.   Amroth pointed it perfectly-there is virtually no competition. At least not a legal one. All criminal, shady or heretical organisations can be dealt one way or another. Legal competitors like AdMech, ruling houses and so forth would be prone to internal bickering. Divide and conquer. And if possible and profitable-denounce. Denounce everyone!!!  
 
 
Of course legal trade is also a viable option. You have ship and money...you are like Swiss banker in some post soviet or banana republic. Everybody loves you. New marks of lasgun, qualified workforce, rare collectors items, valuable trinkets, delicious mega fauna, new drugs and meds, full assembly lines for like tanks, cannons or whatever you want. Everyone wants either to leave, squeeze last drop of profit from this abandoned sector or just keep being rich like they always been-no matter what. And as in any part of the galaxy there...is...also...WAR! Pirates and their delicious ships and holds full of stolen cargo, rebels, heretics and xenos. And lots of sad, troubled officials that do almost everything to keep peace, stability and their own heads on their necks.

Sound plausible.
Yet it implies that genetic tampering is more common in the Imperium of Man than it probably is.
 
In any case those effects could be gained by chem and cyber enhancement. Which is more common but less stable/more time consuming/more expensive.

Brass prism don't answer questions...it helps solve riddles...any riddles. It's like super boost for your intellect.
 
But there is something in the fluff that match-Ragged Oracle, eldar device on the Seedworld AFG:218. (The Radical's Handbook).
And guess what...it's accesible via webway gate at the climax of Lure of the Expanse campaign 

I can't remember off the top of my head but I think Askellon still has many areas unexplored and unclaimed by the Imperium in which a Rogue Trader could operate. Also the lack of competition in the sector, as most Rogue Trader houses and other rivals move to ostensibly more profitable locales could definitely work in the Rogue Traders favour. Also as the Imperium slowly withdraws this does have the benefit of giving the Rogue Trader more and more freedom as time goes by.
 
With so many fallen alien empires to explore and a flourshing trade by the Faceless Trade the Rogue Trader could use this as a basis for profiteering. Exploring and looting planets far outside or the Imperium's borders and selling them to Faceless Trade representitives well beyond the borders can lead to a lot of profit whilst still letting the trade take most of the risk as they will be the ones selling the items in Imperial jurisdiction.
 
Possibly other endeavours out of Hostile Acquisitions might be well suited a Rogue Trader operating out of the Askellon Sector too. An unscrupulous Rogue Trader might find himself with quite a powerful self contained empire as the light of the Imperium slowly fades.
 
Don't get me wrong I think all arguments above are valid but I'd rather answer the OP's question about what the sector might have to offer as opposed to looking at what issues others might have with it.

Why do you even think that the Battleship is the best thing, that the can lay their hands on?
Think of Dark Sovereign, powerfull,agile,stealth warship!!!
 
And why on a Golden Throne you want to START your campaign in the 41K?
Your PCs do not belong here.
Start the campaign IN THE MIDDLE OF HORUS HERESY.
 
Remember how Lorn Orpheus was send from Terra to scout the Pale Stars.
Send your group in the middle of nowhere, let them do some heroic deeds, let them fail horribly few times, let them taste some personal tragedies...
They can save a group of Blackshields/Shattered Legion (some loyal Thousand Son? loyal Word Bearer? Night Lord? Alpha Legionnaire? what an amazing role playing opportunity).
Flesh out as many marines as you can and show some differences between cunning and unorthodox RT crew and Astartes. Let them save the day when regular Astartes way of doing things is not nearly enough.
 
Wanna SuperSnowflakeDeathstarShip...let them capture it.
Play the battle in a way that:
1) leave their ship badly damaged,maybe even crippled
2) through stellar hazards and/or battle damage destroy most of offensive capability of enemy ship
3) board it
 
Now with every piece on your chessboard right in place, give them a mission.
Save a planet, assasinate a Primarch something grand that can save billions of lives,change the course of this war...and throw them in the 41 millenium.
Can you feel it, You ROB them of their DESTINY They should be FURIOUS!
And then go with part 2 of your campaign like nothing happened 

What rule are you basing this off? Because in the book unpowering anything does not improve your speed. Freeing up excess power is not going to magically make your drive tubes pump more plasma than they can by themselves and the ship's superstructure isn't going to survive maneuvers faster than what its hull can take, which means that Eldar Cruiser is going to run circles around it.
 
Also why are you referring to it as "your" ship and "I" can do this and that with it. Are you playing the game or your players, because currently I'm a little confused.

This is boooooooring.
You want to give your PCs power to conquest not only worlds, but sectors yet you give them no purpose.
With all that power you will let them loose to simply goofing around?!
 
The are not only threat to anyone but also to themselves.
Everybody will try to kill them and they will have every reason to do that.
Starting with all those Blackshields. Why do they even acknowledge orders from  someone like your PCs.
They will became target for every traitor,demon manipulator,xeno,and all authorities and organisations of the imperium.
 
With great power comes even greater responsibility.
 
Your campaign have powerfull ship, best possible troops,wealth and ancient knowledge.
But it lacks PURPOSE.

I tend to gravitate to CC so my elite gonna be heavy shock unit.
Though other PC may like them as scouts, tactical or heavy support.
So they can hand pick specialist of our regiments to their personal unit the way Space Wolves chose their Wolf Guards.
I want to have crew and soldiers so skilled, equiped and bloodthirsty that Chaos Revers will rather flee than face them.
Hmm, heavy, elite, CC unit...riding Aethexes...brutal ^^

Let's assume that you have access to any and every piece of equipment from all W40K settings. Weapons, gear, accessories. But only those that you can carry by yourself, so no vehicles.
What would you take to slay:
"Heavy oponent"
Demon Prince, Tau Battlesuit, Dreadnought, Carnifex and so on.
"Super heavy"
Imperial Knight or Titan, Tyranid Titan, Greater Deamon, Ta'unar Supremacy Armour and so on
For example flip belt, warp spider jump generator, this device from BC that disrupt power fields and tons of explosives to wreak havoc inside an Imperial Titan.
What's your ideas?

I tend to gravitate to CC so my elite gonna be heavy shock unit.
Though other PC may like them as scouts, tactical or heavy support.
So they can hand pick specialist of our regiments to their personal unit the way Space Wolves chose their Wolf Guards.
I want to have crew and soldiers so skilled, equiped and bloodthirsty that Chaos Revers will rather flee than face them.
Hmm, heavy, elite, CC unit...riding Aethexes...brutal ^^

Nah, there is no fun in it.
As I remember you can use only one field of any type at once.
So...dual heavy weapon wielding...hmm...nice.
Sadly I could not find any rules for volkite weapons.
I totally agree, my dream is to outfit and train private equivalent of SoB with muscle grafts,black bone bracing, lostok body modyfication (in Inquisitors Handbook there are gland cyebernetics ready to buy) psychoindoctrination and whatever else I can lay my hand on.