My perspective using Nix is that it's hardly worth standardizing ISAs. Recompiling software is easy and we should have a Cambrian explosion of different designs.
This is especially good if one scopes out a family of ISAs that are ABI compatible such that one can compile down to a semi-pre-optimized portable IR, and just do the last bit per ISA.
What exactly does a bespoke ISA buy you? What will justify hundreds of engineers writing a new good one & working through the compiler support?
I bet it would be pretty easy for a user to interoperate between 67 different drafts of the HTTP spec once they were all written, validated, and library implementations coded. But what would that Cambrian explosion of API revs actually get you?