- @Umbran: Hold (Ready, I think) Actions
- This is the closest to the solution that I'm using. The only thing is that, theoretically, Ready actions are only combat actions, so combat must have started for them to be used.
- So this is one of my very few departure from the RAW, I allow characters to ready actions outside of combat.
So, I'm glad, because I find part of the objection to this to be... torturous rules-mongering, no matter what Jeremy Crawford thinks.
In the rules Ready appears in the "actions in combat" section. However, Cast Spells, Help, Hide, Search, and Use Objects are all things characters can clearly do outside of combat, so merely appearing on the Actions in Combat list doesn't mean you can't do it other times! While Crawford has his take on it, the rules a written don't explicitly prohibit it.
The stronger argument, though, is that, "I ready to pull the lever as soon as the Evil Duke enters the room," should be a perfectly cromulent declaration for your character's action. Any rules interpretation that does not allow for such needs to go into the ashcan.
If that's not enough, we can note that in the case of ambush, the Readied action
won't happen outside of combat. Bob says that he intends to start combat. Jill readies to go after Bob. John readies to go after Jill. Sarah readies to go after John. None of the readied actions will happen before Bob starts the fight! It's fine!
For those who are supremely picky, we can note that this can all backfire spectacularly if Bob doesn't get surprise.