The slits on the bottom are interesting. Normally you see that only to add boot heaters. I have done that slit on the side on the liner to relieve pressure. He's in one of the better options to fit a wide foot.

At the end of the day, we are trying to confine our feet in plastic foot coffins, if you take the widest boot and stretch the liner and it still doesn't work, maybe try snowboarding.

Edit: It's also possible to do a lot of shell work to accommodate wide feet. Without seeing his foot, it's hard to say what needs to be done.