@dreman9999: I think what the Thanemancers here are wishing is just a OPTION, a way out so that Thane does not die in game, pretty much like what the rest of the LI's got. If you're arguing about something that is 'canon' to the ME3, then you can pretty much treat it like the story arc of the Krogans (Wrex or Wreave, genophage cured or not cured), Rannoch (Quarian dies, Geth dies, or achieving Peace). Each path is different but every one of them is valid.
This is just my idea to save the ache of the rest who adamantly wants Thane's fate remain the same, why not just treat it similliar to Miranda's romance arc? (If you tell her it's over then she dies at Cronos). Unromanced/break-up Thane will pretty much be the same, no change at all. While a romanced Thane gets an OPTION to be (somewhat) saved (maybe something just to prolong his life although not a complete cure). Make his 'search for cure' mission a timed mission too, so at the end of the day the players will get 3 outcomes:
1. Thane dies protecting the Salarian Councilor
2. Romanced!Thane dies peacefully (or dies during his specific mission to add a sense of 'a little too late' on it) but other Drells benefit from said mission
3. Romanced!Thane lives
This is about shaping a story (where a lot of weird stuff happens but we still enjoy the ride anyway. One example is Shep being brought back from the dead) and your story will no doubt be different than mine, we have different Shepards and different ways of interpretating the ME Universe that Sdhepard lives in. And my principal belief on RPG is and will always be: the more choices there is, the better.
Pls don't take offence, this is just my 0.02 creds only
PS: If my ideas are poorly worded, I appologise. It's difficult typing a whole block of lines here when you're typing with a phone :/