Please bear with me on a long post:
TLDR: game balance matters both for individual ships and between factions, and the age of a ship design probably effects how they could be viewed in the universe -ie look at everything when its new, versus what is also new then, and make similar roles in different time periods fall within a similar range for stats and cost. Finally, at the bottom, I have a framework for the Venator.
It seems that there is some ambiguity on how ship design can work, or should work, or how it is done.
To me, it seems to boil down to some different perspectives:
the first - everything is going to be compared to Lore, ie a Venator is larger than a Victory, but isnt as heavily armed, then the Victory was used by the Empire, but was outclassed by the ISD, during the Galactic Civil War,
And the second - game balance and playability matters more than Lore.
IE: lets consider the ship-building archetypes and the pool of available ships for a faction, then put the ships into a position in the faction where they make the most sense - this plan then looks at ways to differentiate the ships within a faction, and how the factions differ from each other.
For instance, a comparison of the Home One MC80 and an ISD2. Both are main line combatants, but have different strengths and weaknesses, and carry out the role differently, but they both fit well in the main line combatant role for the respective factions (and the factions are arguably balanced against each other when considered at the "sum of the parts" level).
Honestly, I could see the Venator as a large based main line combatant, where FFG chooses to arm and equip the Venator to fill that role in the game (ie with stats to face off against the ISDs and MC75/80s, but I would also expect that it would do so in it's own way). I could also see the game design created in such a way that the Republic Victor Star Destroyers have different stats than the Imperial VSD - since it could feasibly hold a different role in the Republic fleet than in the Imperial fleet. (And likewise for the Pelta transport and Arquitens cruiser)
If folks who advocate for Lore based considerations for stats, over every other way to consider stats, need a way to justify the difference in ships, perhaps 2 comparative analyses of the ship could help justify the change, first in its original role/configuration versus the typical opposing forces at that time in Star Wars history, then a 2nd analysis of the ship role/configuration compared to the newer opposition.
I'd be willing to bet there is some differences identified between the results of the 2 comparative analysis exercises.
Personally, I would guess the Venator would have offensive firepower (in dice) similar to the Rebels Liberty-class MC80, but have a nav chart more similar to the ISD. Maybe with 2 officers, im not sure if it would have a weapons team or support team, but I'll guess at least one variant will have both an offensive and defensive retrofit, and potentially a turbolaser and Ordnance refits (for a total of 6 or 7 upgrade slots if it gets 2 officers). Command 3, Squadron 5, Eng 4, with Brace, Redirect, and 2 Contains?