These are just some suggestions I thought of that could potentially improve the game and add a lot more new content to explore.
1. Make it possible to bring the metal dude that teaches you how combat works, alive or dead, through the juice door and be rewarded for it via either new dialogue if he's alive, or a boost to your juice count if he's dead via sucking his corpse up.
2. Make the evil cave much harder to access and much larger with several rooms to explore. Perhaps hidden by multiple juice doors like in the beginning of the game?
3. Buff the Creator to make him a worthy challenge for players, even with decent stats.
Slightly nerf flight because it's extremely easy to gain infinite and extremely fast flight, but buff walking speed as a compromise. Or maybe just make flight more expensive?
4. Give players incentive to spec into flight other than making it easier to move around. Maybe add floating structures like the planet-like orb you start the game in that are locked behind juice doors.
5. Expand the Fox in the graveyard and the old man in the shack to be fully fledged characters with a bigger purpose in the game's lore.
I will add more suggestions as I think of them. Just keep in mind that these are suggestions and NOT demands, so there's no pressure whatsoever. This is your game, Fishlicka, do whatever you want with it.