I've decided on gameplay now, it'll be the "combat" of Umihara Kawase, while the game has a Rodland/Bubble Bobble-like structure of levels and hopefully 2 player like those games.
Basically, you'll have a simple rope (not springy like Umihara) with a lure(crystal) at the end, you throw it out there and try to hit enemies. Hitting them makes them hooked, and you can reel them in to damage them.
A hooked enemy takes damage from touching you, but it's vice versa with unhooked enemies.
Damaging an enemy will unhook them and push them away so you'll have to hook them again if they have more HP.
So, kinda arcade-y action centered around a rope-gimmick. Hopefully with some cutscenes inbetween levels and of course lavish transformation sequences.