I do know all the little snafus you're talking about.
I would wager that the right wall over-extension is fixable in the config.txt, well in fact I know that it is.
As for the way the area map is displaying - the small pics all appear normally? The backdrops? The Walls? Is this a new issue? If the answer is "yes, yes, yes, yes" or "yes, yes, no, yes" it's the config.txt that needs to be tweaked.
The main reason that I wanted to do diagonal walls for the square viewport (other than adding that ability to the portfolio of possible walls) was an interim step on making a 3x3 round room.
It's not going to be an arean, but combats may occur there, which raises the issue of how to show a round room in combat mode...I don't think we can do that and have the blockage match up, but we can "round" the corners quite a bit.