I played all Banjo Kazooie games.
My idea:
I think the B up will have 2 features, jump and flight.
For eggs, more you stay on the B button and more it's powerful eggs? (fire, grenade, ice, Kazooie Clockwork)
I really like both of those ideas. Since gold feathers are being incorporated, I'd hate to have that asymmetry with no red feathers (it's difficult to come up with a non-broken way to use red feathers, but after Hero there's no excuses
). I like the idea of having five feathers, and for each small flap you lose one--one flap barely makes you jump, whereas five flaps or a beak bomb gives you the same height as some of the higher recoveries.
Eggs types would be nice to include to a lesser extent--I'd be fine if some are missing, but I like your idea that you're not mapping redundant egg types to different buttons, or it being completely random, but instead having control by charging it. I feel like if we're missing Clockwork Kazooie eggs that's a missed opportunity. Fire and ice are less so, but would be nice to have that elemental variety.
The only move I'd really like would be the Taxi Pack for their grab and throw--I like the idea of stuffing someone in Banjo's backpack, swinging them and throwing them. Much more than the example some give of using a N&B mechanics. I'm fine with small references here and there (like their taunt), but would rather it be a consistent moveset.