[robespierre]

The server for a diskless SGI IRIX client computer doesn't need to be IRIX. But IRIX's software installation procedure only runs on SGI computers, so to create the IRIX share tree that the diskless SGI will boot from, you must use a SGI computer. Using MAME to emulate an SGI Indy is outside my experience. I don't immediately see, however, how it would improve matters.

I think you will sooner or later come to the conclusion that diskless installation is beyond your capabilities and you will need to use a local hard disk or SSD.