now before I get into this I highly doubt it would happen judging they are taller than SPARTANs (warrior-servants at least) It would be nice to see due to my love of the forerunners and if we see them return in the trilogy it could happen, there is potential for it to happen. The only way I could see it being balanced is if they are manipulars or first-form forerunners, but canonically that wouldn’t make sense. They also are physically stronger and such.
I don’t think it will happen, the sangheili returning to multiplayer makes more sense