I dunno Ian, I think I bigger Star Fox game can still be arcade-y and challenging. Seriously, they just need to make SF64 and ramp it up a notch. BAM!
Instead of one mission a planet or zone, make it 2 or 3 missions (ie levels) with a different part of that world. Corneria, the first half of the level in the original game is through a city type landscape and then it ends either over the ocean or over a an empty field. In the next game the first level can be the city again, defending from the first of the invaders. It'll be a railed level (mission 1), story wise you're clearing out the waves to buy some time for the Cornerian military to set up a proper defense. Challenge wise, your score determines the next level - Take out too few enemies in your first fly through of the city, and you have to stay within the city limits and help with the defense. This will be an all-range level (missions 2) ala Fortuna. Not only do you worry about getting into dog fights with some of the stronger enemies, but you have to defend key spots under heavy attack. Instead of the bomb scenario of Fortuna, certain buildings or zones have a survivor meter; the longer it takes you to eliminate the immidiate attacks on that location, the more the casualties thus the worse your score. Bam!
3rd mission, still in Corneria, let's go!
Level 1 - Mission 3: back to the corridor, this time you're racing through the more natural landscapes, storywise it would be to attack the invaders head on, aka boss time. Depending on which way you went for your second mission, you either end up in the forest (all-range boss fight at the end) or through mountain valleys (like when you follow Falco through the waterfall). ****, honestly.. it's been so long since we've had a good Star Fox game that I'd give Nintendo the free pass to completely re-do SF64's first level; Race through the mountain valley to cut over to the ocean and take on the boss (which was already lifted from the SNES game) or fight the giant mechanoid in the fields. This would totally be acceptable if the game follows these examples of expanding the gameplay.
If they do that, bring back the speed of SF64 (none of that floaty Assault BS), have great local and on-line multi, this game would fucking work. The beauty of branching paths in the manner explained above is not only does it extend the game a few extra levels, but can make the game simpler without babying the rest of us. You go in, you rock the **** outta the level, and you follow it up with one at the same level or slightly more difficult. If you didn't do so well, the follow up level is all-range where speedy maneuvers don't matter as much, letting you get a hang of piloting your craft. Having big targets that are practically motionless while their attacking a certain building or site; that's letting the player work on aiming while they pilot by giving them much more breathing room. If you miss you can just circle back and keep attacking and you learn how to focus on a target while also evading the smaller threats. It's so simple.
Also, the more branching paths, the more replay value the game has for single player, especially when some stages can only be reached by taking certain paths. Same **** as SF64, just expanded upon. No you have a longer game if you choose to, or a quick arcade shooter if you want to blast through it (pun intended). Change the story up a bit depending on which missions you perform, your endings are different but no "bad" ending, so that you don't feel dissatisfied if you beat it on the easier paths. Maybe have certain team members leave you for a few missions, so that if you take a certain path, they might not be with you at the games finale, or something within the story makes you as the player question what exactly happened and thus want to go back and replay the game with the new route.
oh oh random thought about specific wii u gameplay ideas: if they want to do that path drawing stuff form the command games, please leave that to some sort of bonus mini-game.. I don't want that in the main game. ****, make that a Battleship-esque on-line multiplayer mini-game. Each person plots out a course which ends with a dog-fight. Point is, leave it out of single player.