That would be some miserable shit. Hell, modern day warfare doesn't include this sort of tactic anymore.
I've only had to dig fox holes in training, but I can tell you they're not fun to be in most of the day and for damn sure not to sleep in.
I remember one night during an FTX on Ft. Lewis having to sleep in one I dug and this goddamn relentless mosquito would get close to my ear with a megaphone to blast his buzzing sound. I tried all night to swat and kill that fvcking thing but to no avail.