I spent some time looking at all the different things I can do with the movement engine, it's pretty fun. Unfortunately I took down the wall climbing, wall grabbing and wall jumping; but I kept the water, hills and springs. The hills don't have to be diagonal, they can be curvy and round and they still work.
Apart from that, I've retrofitted all of the movement so that when you press the S key "time" freezes, and then when you press the S key again everything resumes, including previous momentum (which means if you pause just before running into a wall... better brace yourself for a collision when you unfreeze time).
The pause screen will be where you select an attack for battle, which will otherwise be in Real Time. I think I'll check out Tales of Phantasia and see how they did it, since Jon222 suggested that I might find it helpful.