I really hope they expand the characters a bit more, as they are right now Star Fox characters are kinda boring yet they can very easily be put into a comedic scenario. Fox could be the pit of the game, constantly joking around, not really taking things seriously, Krystal could be the palutena, giving guidance with a hint of sass. Falco could be cocky and jealous of fox, constantly wanting to be the centre of attention as well as putting down the others and judging them when they do something wrong. Wolf could be very sarcastic and snarky. Slippy could be slippy. Leon could be psycho etc etc
Also I want a female star wolf member to rival Krystal that would be *****y and sassy as ****
They already have quite a bit of established character to work with. I wouldn't want them to try too hard, heh. 64 did the best to establish their characters. Fox was the leader and relatively professional and serious. Falco was brash and cocky ace that liked teasing Slippy. Slippy was inept and silly, but a mechanical wiz. Peppy was the old vet with "sage wisdom". They all fulfilled a certain character trope so as to play off each other and balance the personalities of the team.
Play Adventures if you want to get a better feel for a fun Fox though. Assault and 64 made him fairly flat with some moments scattered around. His expressions and reactions were great in Adventures. Assault's campaign was fairly serious for the characters, but the multiplayer shows a hint at their more fun halves... except Fox, he's still mostly flat there. Just watch their idle animations. Falco grooms his "hair" with both "hands" for instance. Even just that behavior says something, lol. Their taunts as well and victory animations. Even though Adventures mostly features just Fox it also does well to develop the other characters the few times they are shown or interact. Krystal could use some more development though. Her appearance in Adventures mainly has her as headstrong and caring and eventually somewhat flirty with Fox. Although, I think she actually likes making Fox uncomfortable since she finds it amusing as much as actually liking him. Her appearance in Assault does a bit more to show her character. She kind of is the one that diffuses the arguing between Falco and Slippy so she's a peacekeeper. More than that I think the multiplayer gives us a better hint about how she's also fun though.
Smash also has some stuff that shows them being fun and more interesting. Listen to the back and forth in the cameo appearances at Orbital Gate Assault and Corneria on 3DS. There's character there waiting to be expressed. There's details about the characters that can be fleshed out. I wouldn't want them to try to develop them too much like Command. That approach to them felt like a mistake. Plus that game just wasn't that enjoyable. They should be ragtag team of mercenaries that's not too serious but each is unique and brings something special to the team. That's pretty much how they are now, just not as developed and expressed as they could be. I think if more than just Fox is playable in the main part of Star Fox Wii U, we could have a chance at some unique dialogue and gameplay, especially if there's an emphasis on improved on-foot missions.