Imo, god should be careful with the idea of making himself no longer omnipotent. At the very least, he should retain the option to make himself omnipotent again just in case. Can a non-omnipotent entity make itself omnipotent? I guess god could find a way. I'm just sort of warning him about possible complications, I guess.
Worth noting that elves don't have this problem in the first place. It's among the reasons that many elves are happy with their limited superpowers, and not seeking promotion to the top job in the supernatural entity game, even with all the perks it offers.
It would make sense to create something along the lines of an omnipotence button which he can press to make himself omnipotent again in the event that he finds himself in a Spider-Man 2 type of scenario where he needs his powers again because Satan is threatening the city or something.