Is this busted

[Skrum]

Dim light gives light obscurement, someone with the Skulker feat can hide in dim light. Dim light imposes a -5 passive perception.

Doesn't dim light give disadvantage, is that what you mean by -5?

Yes this would reduce the value of Skulker; my skill tricks for Medicine encroach on Healer too. But honestly, I don't care. I really don't like those kind of feats being in direct competition with "optimal" feat/ASI choices, and players feeling like they need to accept making themselves worse in order to get unusual or flavorful abilities.

There are things you could do with skill tricks using stealth, like be detected on purpose at a false position. Or hide from someone you're adjacent to by staying out of their field of view.

Maybe, but I'm trying to avoid massive blocks of rules text too. In the case of the "false position" one, I'm leery of stuff that implies that enemies will take a certain course of action. It just gets funky; how compelled are they to follow it? What actions would they take? It just gets annoyingly murky.

Displacement would be an interesting option instead of invisibility.

Interesting option! Like mirror image, or like blur?