XFl pay scale is going to be the issue with those guys - Mumme is the price point. If not USFL picks him up.
If those three hire assistant coaches that lack much experience in coaching, they are going to look like how Kirby Wilson looks out there in the USFL: not having any clue as to what he's doing. They need at least one assistant who's had a ton of experience, which is why I looked at who their coaches were as players.
Its a good idea, but I just don't see XFL with the $$$ for these guys, who knows.
Plus Hal Mumme knows non-NFL football which as we see can help in these leagues.
This is assuming he wants to coach spring football again. He may just want to coach high school, which would be less stressful.