Is it even possible to write dynamic hash algorithms that cannot be imported easily to perform better on (GP)GPU?
Only if it requires A LOT OF memory.
Ok, thats not feasible. It would be nice if these hashing algorithms could include some 3D/CGI operations so that instead of developing FPGA/ASICS, a better multipurpose graphic cards were developed

That would require all the graphics operations a modern card can do. Or at least a lot of them. Otherwise you can implement it in a cheap FPGA/ASIC. IF you use all of them the die space/gates used would not be worth it.