I haven't got your answers, but will pipe up anyway, because a) This is something I too will be needing and b) If I do, sometimes somebody who actually has a clue, will groan inwards and make a great post to correct my blather. :)
While the whole scripting thing and the logic structures are a complete mystery to me, so far, I think there are clues to be found in the "sitting mods" tutorial in the wiki.
http://www.guildofwriters.com/wiki/SittingModsLogic.modifiers.activators type:objectinvolume certainly sounds interesting - as for triggers, I surmise you'd need no further conditions and there might exist some "always" trigger - dunno. There was also a bit of talk about subworlds in one thread, with an example on how you could trigger subworld entry and exit, by entry and exit to- and from a region.
Hope this doesn't turn you in the wrong direction. :P