Seeking some advice and technical help regarding creation of multicore system

I can't help much but i can offer a point of view.

Running multiple Nios cores will still pale in comparison to having the compression in hardware HDL; by enormous differences.

There is alot of overhead on running C instructions on a Nios. Having a multicore CPU setup could likely be as difficult or more so than converting your C code to verilog.

If you do it in hardware you will use less resources and at the same time Can create more parallel processes that peform much quicker.