As the summer is coming to an end, I've been rushing to finish the game. It'll probably be published here on Newgrounds tomorrow. I reached a bottleneck when it came to world-size. Expanding the world would require a refactor, which I don't have time for right now.
The main problem right now is that scene managment is run by strings, so renaming shit would requrire lots of labor. Save data is string based, which in turn is pretty unstable. Making a massive singleplayer game would require secure data.
Other than that I think the system is fairly robust and expandable. I'm going to look into mobile opportunities, as well as revisiting multiplayer options. I think it would be cool to have a marketplace area that's multiplayer. I also have in mind to redo the world system so it's split into nodes, and then possibly make my own heightmap thingy in 2D...