It's nice to see you have cliffs on your list, but just so you know what I'm talking about.
When you create a cliff for a normal RPG, it's only meant to suit one viewpoint. You don't see the sides of the cliff apart from the front. Wouldn't this be the same in this script? From the screenshots it looks like all the cliff faces are just thin columbs.
My suggestion. Before you go into heavier updating like cliffs, towns and ceilings, wait for that Mode07 script to be released. Then you can use that script to simulate floors, walls, objects and ceilings with perspective.
Also, how's about using the "pop-up" technique, except instead of a picture each popup links to a characterset. So you can have a tree with multiple sides and whatnot, and also the resize sprite script (I know there was one on .org, used for simulating perspective with sprites, namely used with pre-rendered backgrounds) could be used on them so you don't end up with white edges from resizing picture files.