Would it take long to do something like that?
Also, would you care to explain why the chair must be marked as persistent. I don't understand that. Sorry.
It wouldn't be too hard to do, provided you knew how to script. I've looked all through the companion script, but could only figure out the absolute basics of it. It'd be a simple to do, but might require a fairly good grasp of Oblivion's scripting language.
No idea why non-Persistent chairs are a hassle, but from using a few companions that sit when you do, I see no real rhyme or reason to it. It probably has something to do with calling a Package that tells the Actor to target and use a chair. No problems when they're eating, they always seem to be able to sit under those circumstances, only when directed specifically to sit.