[jecel]

By original MIPS designers do you mean from Stanford? Those would include John L. Hennessy, Norman P. Jouppi, Steven Przybylski and Christopher Rowen as the authors of the first papers about the project. If you are talking about the MIPS company started by John Hennessy and Chris Rowen, Wikipedia has this list:

https://en.wikipedia.org/wiki/MIPS_Technologies#Notable_Cont...

In either case, I am not aware of any of them being RISC-V leaders though John Hennessy did rewrite the books he co-authored from DLX to RISC-V.