Reread your earlier thoughts, and I think I see the particular problem here (and indeed one of the general Tau problems). What I think you are suggesting is reviewing the 'normal' Tigershark weapons loadouts to make them more generalist (and perhaps more AP orientated).
I think we are coming round to the specialist variant having something like:-
TigerShark AX-1-0 ÂÂ
Burst Cannons
Twin-Linked Railcannon  - Titan Killer OR sub munitions
Seeker Missiles ÂÂ
What I think I am hearing is that you want to provide an AP orientated
OR AT orientated variant of the 'normal' Tigershark, so something like:-
TigerShark    ÂÂ
Burst Cannons
Twin-Linked Ion Cannon
Twin-Linked Missile Pod
Seeker Missiles  OR  Smart Missile system
So what we are coming to is providing the stats for three variants: AP, AT or the AX-1-0 TK variants. Obviously we can resolve the actual stats later, but I would suggest they should work out something like this:-
TigerShark AX-1-0 ÂÂ
- TK variant
AP hits ~2 (but MW)
AT hits ~3 (but MW)
TK hits ~5
TigerShark  ÂÂ
- AP variant
AP hits ~4
AT hits ~2
- AT variant
AP hits ~2
AT hits ~4
Note, I would be very cautions about presenting too many options because in doing so, you will blur the distinction between the two main A/c variants. Indeed, I would suggest that you could actually achieve a similar result by permitting formations to comprise different variants and weapon configurations.
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The other issue I think you (and Hena) are expressing is that you see relative costing of the 'normal' Tigershark being less than the AX-1-0 variant. I am presuming that this is because of the relative rarity of the AX-1-0 in the 'fluff'.
Ok, here, I would suggest letting the player make his choices, freely if possible. The improved Railgun TK stats were suggested both to make it more specialist and also to allow a reduction in the 'normal' stats. Yes the player could choose three such formations (for 900 points) and indeed they may well be able to kill a big titan / BTS (assuming they do not fall victim to enemy AA); but then they will have an insignificant impact on the rest of the enemy, cannot take objectives, and the player cannot have any other air formations (like Moray etc).
It is my contention (and intention) that the cost restrictions imposed will self-regulate the use of the Tigershark in any format; which is one of the reasons for suggesting a target cost of 275-300 points (and which incidently approximates to other bombers etc). The logical conclusion to this line of thought is then to give both variants the same cost.
So, while I understand your concerns about letting both A/c have the same cost, I would contend that if we make the AX-1-0 very specialist and the Tigershark very generalist (via optional weapon loadouts etc) this will actually guide the player to self-limit the use of the AX-1-0 thus matching that aspect of the 'fluff'.