Not that I know of.
Ah, my mistake then. Thought it was something like Nassana's quest. Couldn't remember.
It's hard to tell exactly what options Tali would be needed for.
Again, I guess it depends on what happened to her during the trial.
I think it's safe to say that having exonerated Tali alive (especially if the evidence wasn't revealed) would increase Shepard's influence over the quarian government.
More than any other quarian yet, Tali has the most balanced position on the geth-quarian issue. Particularly useful is that she's of the opinion that the quarians should focus their efforts on the reapers. All of the admirals seem to be caught up in their own agenda (though who knows what Shala thinks).
Indeed. Though, at the same time,
if the Geth network has been influenced by the Reapers again (which, apparently, at least some have), then it might be difficult to do much of anything with yet another threat at your back. Their conflict will have to be resolved one way or another, even if Tali suggests concentrating on the Reapers.
(As far as I can tell, Shala seems to be a "I'll go with whatever way the wind is blowing, since I won't really have a choice," sort of person.)
It's also possible that Tali's mechanical expertise would come into play.
Quite possible. She's already helped upgrade the Normandy's shields for the Suicide Mission.
Actually, when you think about it, Tali was an optional recruit, yet, her shield upgrade was far from optional if you wanted to keep everyone alive.
Maybe it will be something similar in ME3. An optional character (since she could have died in the suicide mission, though no one here killed her, I hope :stares:), but with a less than optional role if you want everything to turn out 'well'.