About your last point, in the latest version I am working on you retrieve all keys on death and at a checkpoint, so it’s way more practical. For the rest, I prefer to keep the control scheme as simple as possible (which makes it way easier to design with) and focus on external mechanics, like the shooters, that makes you use the keys in a new way. Thanks for the suggestions !
Makes sense to me! Actually, the way you phrased that made me think of some very different mechanic ideas. The main one is adding some sort of gizmo that moves all your placed keys when you run into it. Something like an arrow that could face up, down, left, or right. That would add lots of possibilities, especially combined with common mechanics like push-able blocks and various sorts of switches. Also, lines of arrows could turn the placed keys into an interesting version of moving platforms.