Sadly I wouldn't know enough about microarchitecture to understand whether nanocode would actually be a benefit. surely if CPU's became big and complex enough there would be a benefit to have hierarchical translations down to micro-ops and smaller subdivisions for execution units. What you're describing seems to come close to FPGA's. The possibility to write very complex sequences to pipeline different payloads trough the system while maintaining proper state. Though I think the economical solution might be more boring, the intel ME and AMD PSP hardware is probaly responsible for alot of management of state that could flush or change how instructions are executed with very basic logic.
If esoteric hardware interests you I would recommend IBM system/360 as reading material. Sadly hardware like that has fallen out of fashion and we've been stuck with the x86 and arm dichotomy. if anyone else has interesting/newer non-x86 hardware to link I'm more than happy to delve into that.