I look forward to it.
I would still keep a one key menu, and one key for virtual keyboard one for mouse mode - that still leaves 5 keys, with an emulator like this you need quick easy access to the extra functions - for mounting disk accessing options etc - say select for menu and start for virtual keyboard. It might be worth have a "keyboard" function for the joystick as well so that games that used keys only for control (there were some) could have keys mapped to dpad. Similar to the Spectrum emulator's - cursor function.
5 mappable Keys will be more than enough for most games - and with quick virtual keyboard access - pretty much everything will be playable to some extent - If you can make it save and load a config for each game then we're laughing.
Once again great work, and depsite my Amiga fanboy nature I reckon you are right to develop this rather than move on to something else - better to have one fully (well mostly) functional emulator done.