It will separate from the metal and start rusting underneath where you can't see what is going on.
This would also be my greatest concern. All of it will separate to some degree and I hate Herculiner. I did put some Turboliner on the exterior of my 3B. I ran a strip about 2" wide around the the side of the tub and on the rail where the top snaps down, and on the cowel where the windshield sits. All the places I couldn't keep paint on. I also did the hood as we are inclined to throw boots and other stuff on there when out in the boonies. It also cut the sun glare. Tubroliner isn't quite as obnoxious as some of the liners. Fine textured and relatively hard.
I'm not big on diamond plate either but did make my front fender support/steps from it to minimize slipping when standing on them.
The absolutely most ugly Jeep I have ever seen was a 2A completely coated with red Herc. At least it was good camo for vomit.