Funnily enough, up throw was the main thing I was thinking of when thinking of moves Tails could pull from Sonic the Fighters. In that game he has a move where he just picks the opponent up, flies up high and drops them. Could adapt that into a Kirby- or ROB-style up throw for Smash.
I don't particularly want the guy myself, but I do think there's a lot of cool potential for Tails in Smash with regards to an interesting fighter and a beloved character and I reiterate I said before - having Sonic playable, Knuckles as an AT, but no Tails at all, would be far too weird. You surely should have all three prominent, not just two. Surely?
I think Tails is a very strong candidate for playable, his personality and skillset translates into a playable character for Smash a lot better than that of e.g. Knuckles in my opinion (you'd have to give Knuckles things like gliding for it to be Knuckles, and they dropped that mechanic for a reason...). So yeah, nobody's a lock, but if I was about that life I would bet on Tails at this point.