Even though I'm far from needing this myself, and that list of yours must already be rather long, I thought I'd better mention this before I forget or some else has problems with it.
Suggestion: Allow user to set which screen angle the game uses for selecting diagonal loops.
Just allowing ratios, x/y in [1..5] would probably be sufficient for most cases (any higher wouldn't have much use for diagonals anyway).
As I understand it, the diagonal loops use screen angles near 45 degrees.
The problem is that the angle at which rooms and characters are typically viewed is very far from a plan view, often almost a side view.
Under this aspect, a 45 degree screen angle corresponds to slightly left/right of vertical world angle, and isn't really useful.
(I thought of a way to cheat in the correct loops for a given aspect ratio using existing features, but it made poor use of resources.)
I asked for this a while ago, it would be a useful thing to have, it would complement the new seperate x/y walk speeds very nicely.
Interesting idea. I'm a little unsure how it would work in practice but I'll have a think about it.