My intent is to make the dungeon and walls look similar to the one done by Caveman over on the Hirst Art forums:
http://hirstarts.yuku.com/topic/1269/The-ever-popular-modular-fieldstone-dungeon?page=1#.UpIuq-KrEv0
His is not based on HQ, but I liked his wall design the most out of the one's I've seen. As far as the miniatures not fitting through the hallways, the Caveman walls are have 1" bases, but are only 3/4" thick, leaving that 1/4" to the corridors. If that is not enough room, then I suppose I will have to turn the miniatures sideways like I currently do. My future plans are to indeed make a modular board (I find it quite annoying to have to make room for the entire board, only to use 1/2 of it during a dungeon). Plus, I think the modular dungeon gives it more exploration appeal. However, my wife suggested that I start small and just try to get the basic board done before I start doing anything too complex, and I tend to agree.
I hadn't really considered the effects of the hallways getting longer due to the walls. Can anyone explain the cons to that? You say it's not compatible with the Quest maps, but what issue other than having to move your pieces further have you run into (My wife and I are only up to quest 7 of the base game, so we haven't experienced all of the different scenarios yet).
After several attempts to fix the 2x4 rooms and put a wall in between them, I came up with nothing and did what the others have done by merging them. With the modular version I plan to do, that will be solved.
Thanks again!