With an ARMS rep getting added, even with Spring Man as an Assist Trophy, it gives me a glimmer of hope that Waluigi could get promoted to a full fighter.
That being said, I’m hoping for the last 5 to be:
Crash Bandicoot
Doom Slayer
Geno (Super Mario RPG)
Rayman
Waluigi
But I could also see Rex and Pyra, Travis Touchdown, Ryu Hayabusa, Bandana Dee or Dixie Kong.