MesaMan

Boy, a couple of answers were immediately obvious to me. Allysen hit the primary one: you want to have control over what is taken. Not being there; having a helpful Neighbor stand in for you; or you being in the Yard are all mechanisms that take you out of this desirable control mode.

Even with, say, an Items List you've provided, when a Neighbor steps in to prevent the inappropriate taking of something, you wind up being dragged in from the Yard to mediate. So, the emotions already will be cranked, and you wind up in the middle of it anyway. Especially if they've gotten a buzz on prior.

There likely will be the motive of 'punishing' you via taking things they suddenly think they're entitled to. If you don't think this will go down, you are saying they will exhibit reasonable judgement and it won't go down that way. And, that is a reasonable expectation of them just why?

Regardless of how detached you might feel about certain items, one 'gift that will keep on giving' is the residual pissed_off_ed_ness you will have to process when, despite your careful plans, items that shouldn't have been taken are taken. I think this will be like getting over hurtful words said in a drunken fight. Yah, now, items taken illegitimately are only possessions. The act of taking possessions will itself become a new wound to process.

If you can't be there, you can't be there. Your call, obviously. It might be one of those things in Life that is worse to think about in advance than to actually go through. Pre-separating his Possessions and putting them in, say, the Garage removes most of the angst and inevitable conflict of 'real time' sorting and decision making. If items are pre-separated, then having a Neighbor simply keep them out of the House, or out of certain areas of the House, becomes part of a reasonable solution.

See the Post of Recovering2 above. By being there, you take your power back.