My concern with nmigen with a taped out design isn't that you can get it to pass the PDK rules. It's the difficulty in creating a productive feedback cycle once simulation shows the inevitable bottlenecks in your design for each process node you're targeting.

It's for sure a solvable problem, but 9 time out of 10 the FOSS developers trying to push a new language into this space end up not meeting their actual "release a usable design" goals but instead spend all their time yak shaving the language. It's a classic nerd snipe in the space.