Revising my votes:
+vote:
Issac
Ridley
Goroh
Dixie
Pichu
Issac because Golden Sun could use some Smash Bros. Love. Goroh, Dixie, and Ridley, because their games don't have too many playable characters represented. Pichu because Melee, and he could be interesting, funny, and a thrill to play if revamped properly. P:M is the PERFECT chance to rescue Pichu from the scrappy heap.
1/2 vote:
Paper Mario
Lyn
Tingle
Lip
Knuckles
Paper Mario and Lyn are great choices that just barely missed the plus vote since their franchises are pretty well-represented as-is.
Tingle would be a pretty funny joke character and he's definitely the best Zelda choice IMO. If Lip doesn't make Smash 4, I think she's also long overdue for an appearance in Smash as well. I don't think Sonic really needs any more characters, but if anyone else gets added, I think Knuckles would be the best pick.
Neutral:
Andy/Sami
Toad
Tom Nook
I'm not for these characters, but I'm not against them either. If the PMBR can do a great job with these fighters (which I'm sure they can), then more power to them!
Though let's be real-- as it's been mentioned, the PMBR has probably already picked their choices for upcoming clone engine characters by now...