I was thinking while working on one of my games that there are a couple of things that would be cool to have as interface customization additions.
First is outputs.
In my game, I put 3 lines and it's big enough to fit all 3, however it still displays a scroll bar. Maybe there can be a feature to totally get rid of the scroll bar whether the line limit is set or not.
Another thing can be making output backgrounds into gradients and making text colors gradients too. Also we need some fixed image-background outputs! They show as completely black sometimes when it should have an image in the background.
Next is for the default interface. We should be copying it into their source files and including it in the file. I believe this will make it possible to customize your own interface to have less games looking like "some piece of crap 5-minute game that was made in C++ language class" as mentioned in Silk Game's post on how NESTalgia had success (when it showed the comparison between a good and bad game.)
Now finally is for the last part, the overall interface. I think we should have a button on the overall DMF editor window (The window that shows right after double-clicking the DMF) for the windows created that should control where the selected window appears and disappears during the game, so you don't have to memorize the code. This, of course, meaning that we would need to specify a proc that it would disappear and/or reappear in.