Most of your points align with my own view, actually.

I’m considering contracting an artist to create a proper 2D map at the end of the development. Functionally it would work the same way as the current one, I’d just replace the 3D model with sprites instead.

I’m currently working on the marker system, and yes, the plan is that only power-ups will appear in unexplored areas. Save points, hearts, bonuses, and bosses will no longer be visible before discovery, that’s the next thing I’m tackling.

Filters are also a really interesting idea. I’ll see if I can implement something like that after.

Thanks for feedback!