Ok this might be totally random but I think it might be possible to use the power of some GPUs to offload the heavy lifting. Imagine having a world with lots of stuff going on. It would be nice to have it offloaded to the GPU as the GPU can do calculations in parallel.
I just figured that some of the AI accelerators might be useful. I do hope that Minetest gets better multi core support. Most new devices have at least 4 cores at this point and the newer midrange chips have 12. (12th gen Intel)