How would you design a trick room setting ability?

So people have talked about this for awhile (usually in regard to buffing dialga) but the problem is it would be absolutely busted, so people have put forward potential "nerfs" to make it balanced. This post was originally gonna be an idea I had for it but I thought about it for 3 seconds and realized it was bad. It would be instead of on switch at the end of turn, the idea is that it'd be balanced by it turning itself off and not usable on the first turn. You would think "oh just use protect every other turn" but that makes it predictable when you'll protect and forces you to run it on every mon that wants to use it. Unfortunately it turns into a game of coin flips on whether they'll protect which doesn't sound fun, as well you can get around it by protecting them switching. Maybe put it on a fast mon so it only helps it's team and it basically has truant?

Anyway since my idea fizzled as soon as it formed how would you implement it?

Also using nerfs there felt weird since it doesn't exist yet so it's not "nerfing" anything.