As mentioned, there is a mod that adds a number of magical items which is fairly cool to play with but heavily limited by the game itself. As for the base game, there just isn’t really enough stuff to support an Occultism skill. Intelligence is already responsible for protecting against psychic attacks and artifacts aren’t really fleshed out enough to be properly examined ingame.
A Science skill would be fairly redundant since Electronics, Mechanics, Fabrication and Cooking already covers all the high-tech stuff.
An Athletics skill wouldn’t be a bad idea, considering we already have skills like Melee and Marksmanship. I could even see it replacing the Swimming skill and giving buffs to most, if not all, physical actions. Having said that, strength and dexterity already do that, and I think a fairly large part of the game is balanced around limiting things to what your stats allow, but there’s also evidence to the contrary.
As mentioned, crouching is already being worked on and should be ingame before long. Personally, I’d also like to see a camouflage and hiding mechanic, but we’ll see how that goes.