Nice engine, I'm always interested in engines like this. I've started my own yesterday in c++ using OpenGL. Engines take long to make. I think maybe you should have made your engine completely first before you put this topic up. It looks like you're pretty set on making overworld maps, but what about battling? Have you guys started on that at all? Will it be 3D too?
Does using Lua mean that you're interpreting Lua in your engine? If I want to use an interpreter with a lot of features, I would have just used GameMaker or something of that sort.
By the way, you made your OS look old. lol It looks like Visual Studio 2010 in the background.
Good luck with your project!