I think this game shines best when it treats the different subweapons as pieces to solve a puzzle. I enjoyed the rooms styled around the laser or the axe and figuring out the safest way to progress through the different spawns with the least danger.
I would actually second your idea you had below to completely cut the gravity, I kinda thought the same while playing, I feel you could have a lot more dense bullet patterns and precise dodging if you don't have any drag or gravity, etc. Although that would change the genre almost, but I could see some bullet hell/castlevania crossup working. Either way, this had a lot of cool moments and a good feel to it, good job!