Need some streamlining help

Hey guys, it’s me again and now I am once again asking for your support. I was planning on revamping my towers models in my tower defence game but right now I have to design about 15 rig’s for a tower with 2 paths with 3 upgrades each. I have tried to have one model that just changes accessories but I guess I just didn’t feel it.

How would I streamline this process into something modular?