I'm not sure I want to do that. Even the SDL keyboard input can get a little messy across platforms as I've learned during LandTraveller's 3D prototype. Since this is a tool to make RPG games styled after old console jRPGs, I chose this classic menu. Of course, you shouldn't use it to enter in more than name-sized things.
As an added bonus, this will work just fine if ever ported to a mobile touch device like Android or if you want to lay back and play with an actual game controller.
However, unlike classic console jRPGs and because mobile devices have a touch function, I might (probably will in the future) add the ability to use the mouse (complete with setting the mouse cursor using icon from game). Would be handy if you completely lost your mind and wanted to make a visual novel with RPG20XX.