It's probably better keeping this under House Rules, fits more accurately
Playing any Xenos in Deathwatch is going to be immensely difficult if not impossible purely due to the concept. These are the Ordo Xenos specifically trying to kill your blue/grey arse and any alliance with a Deathwatch KT and a Xenos will be short lived. Radical inquisitor or not, the marines WILL turn on your Tau character and you will end up in the firing line the very minute the Ork/Nid threat is over. I wouldn't be surprised if they dont even start sooner!
However since you're set on this whatever happens then here are some things to consider before I go into numbers.
1) You will not benefit nor contribute towards any squad cohesion, if anything are likely to detract from it. The marines will be unlikely to bond with you and unlikely to allow you to benefit from any tactics or discipline. So consider yourself likely in Solo mode, feel free to come up with tactics only for yourself. Don't expect them to come back for you either, if they are playing IC likely they will be happy to allow you to have an accident in the field and claim you were unrecoverable.
2) You may need to create a Tau specific character progression and XP track to allow you to keep buying upgrades and stay competitive with the rest of them. You will need to consider homebrew of that.
3) Ammunition and supplies will be difficult. Unless you have a small cache of ammo with you or access to a Tau arsenal, do not expect to be able to resupply easily each mission. IG tech will not be compatible with an XV9 and vice versa and neither will they let you besmirch blessed Imperial ammunition on foul Xenos weaponry. Do not be surprised if that supply gets raided. Additionally your repair of your gear will be difficult so care must be taken.
4) While the KT and Inquisitor may be forced to work with a Tau, other Imperial assets may not be so forgiving and may also fire first without asking. Don't expect other Imperial assets to work alongside either.
5) The very minute it looks like your mission is done, plan an exit strategy or one of the KT will put a dozen bolt rounds through your chest plate. This path is not one which will last for long...
Honestly, the risks are very high and it's not worth it IMO.
Concerns aside, now for number crunching:
I brewed up a load of random Tau units here, do feel free to like/hate/incinerate at your discretion but I did add some for XV9s based on stats from Forge World and trying to compare to current 6th ed looking at how they were with the 4th ed codex.
I argue that an XV-9 is not massively better than an 8 series so I would say you're looking at AV8 full however IIRC these have vectored thrusters which could grant the use of "Assassin Strike" talent or similar. You'll count as a big target so unlike the marines, you will be easier to shoot and you can forget being stealthy obviously. The suit though would give you the benefit of Dark Sight like marines as well as things like auto stabilisation but also things they might not get easily like independent targeting, basic flight ability...
Weapons wise I think the 9 series is limited to a select few, I've tried some profiles for them, please take them with a pinch of salt:
Twin Linked Burst Cannon - Standard Burst Cannon with Twin Linked
Phased Ion Gun - 1D10+4 E, Pen 2, RoF: -/-/6, 60m Range, Special: Tearing
Fusion Cascade - 1D10+8 E, Pen 10, RoF: S/2/3, 30m Range, Special: Melta
- Pulse Submunitions Rifle - 2D10, Pen 2, RoF: S/-/-, Range: 300m, Blast (3)
And that's all I can come up with at the mo.
Edited by Calgor Grim, 18 July 2014 - 03:55 PM.