personally,I think it isn't toooo hard but maybe that's because I watched a walkthrough of the game (old ver) from YouTube before proceeding to play until ver. 2.1.2
as you mentioned that we don't really have much options on where to start and experiment, maybe,just maybe, riddles may do the trick XD there are riddle on grave stone in the game, but I only one or two I think. if there are like, 100 small areas in the map, with 20 hidden passages to be found,maybe you could set a few (about 5-7?) riddles, either on grave stone or anything you see fit.
its just a suggestion though. will come up with idea when I get to play again.
on version thing, would be good that you make a new version, update this one for last time and put up a notice for the players to know that the later version of this game is named differently/so. but these depends on which you think is easier to do XD making huge change on something existing could be harder than starting a new one, but it might be vice versa. so, choose as you feel I think.
on map, don't really have much suggestion. I liked how I could travel to world 1, world 2 (sanctuary forest) and world 3. teleportation is fun