Bit by bit here
The Kanto Trainer is pretty popular and has unique mechanic, and the GEN 1 starters are well loved.
This is true, and gen 1 starters are back in the spotlight once again thanks to Mega-Evolution, however, I feel slots for pokemon are well contended, there are other equally as popular, as well as more recent Pokemon who would fit in just fine. It'd also be easier on the Sm4sh crew to have one or 2 totally new pokemon instead of redoing Squirts/Ivy/Charizard and the PT himself.
- Wolf isn't all that much of a clone, despite what people think
I'm still scratching my head as to why Wolf made it in to begin with, honestly. Was it due to the popularity of Fox/Falco in Melee? I've played Starfox, and Wolf is cool! I like him, just, in Smash? I never once considered him a contender, and I'd be floored to see him come back. Chalk this one to personal taste.
- G&W is a two time veteran, do you have a reason for this one?
Ness was going to be scrapped for Lucas in SSBM, I don't really feel Vet. status would apply to G&W's chances. I feel they've done what they needed to with him is all.
- ROB is an important figure in Nintendo history
Yeah, I'll give you that one.
- Lucario is still a popular pokemon
As are Zororark and Sylveon. It'd be easier to replace Lucario, who was more of a representative for Diamond and Pearl, than it would be to replace Jiggs.