Awesome job so far Wheybags!
Are you going to use a library for the Gui? I know Stratagus uses GuiChan
to make their UI and I think it looks really well done. Are you looking to be creative with the GUI and rethink it for 2014 or are you trying to keep it as traditional as possible?
Your vision would allow mod makers to create their own GUI for their games, correct? Are you going to separate out the appropriate files into .lua files? I read on your GitHub issues page that you want to use Python for scripting. Would this allow separate files for things like quests and dungeons?