IFTW doesn't change target (manual target is needed) and doesn't "auto-cast" innervate, so it's basically compliant with the new Blizzard idiosyncrasies.
The only thing it does are:
1) check target class (no more really needed, could be useful)
2) check target mana - if below x%
3) if 1 and 2 are true, try to cast
4) according to the cast results (success / LoS / no mana / out of range, target dead) announce something on different channels (say, multiple configurabel channels).
BTW, Decursive actually cast spells form the spellbook and doesn't seems to be affected by errors. I'll have to check it better tho... let me find something that can poison me
Anyway, even a "new" button with hardcoded spell could do, provided that it can do the same checks as above, as is check class, mana percentage and announces. Autotargetting is NOT required nor useful, I don't want to innervate a shadow priest, locks or mages just because he/she burned his/her mana.
Oh, 4got... IFTW of course had the self-cast feature, aka with a modifier key you could cast on yourself no matter what.
If you find a way to replicate that, let me know. I can code and debug, but unfortunately I know very little about frames and such... I'm an old, plain console programmer
Cheers, Arz