Why would you want to overwrite the sprites during runtime? Understanding your use case would help me evaluate if that’s a good fit for the engine or not.
I have been thinking about a game like Worms, with terrain destruction. The terrain would be kept on the sprite sheet and would be drawn with the sspr function. I can check for collision with the get_spr_px function, but I cannot make changes to the terrain, because there is no set_spr_px function.
I have made a similar game for PICO-8 and it allowed me to remap the screen and sprite sheet addresses in the drawing state, so I could manipulate the sprite sheet during runtime.
Could you use gfx.px instead to draw the pixels? Here’s an example that shows how to re-render a sprite pixel-by-pixel, which i think should allow you to do what you’re looking for: https://codeberg.org/brettchalupa/usagi/src/commit/cd7822d9dd26aac9ea01c970aa5ca90dac58cc4d/examples/px.lua#L70-L83