Mainly based on how NES emulator Nestopia does things that are unrelated to NES/Famicom itself, so if you have used it before, you can skip the thread to the next post that has other suggestions as this one basically "make it more like Nestopia"
- Menu bar for opening roms/setting configurations and so on
- Video config with stuff like ability to set a filter such as scanlines/simulating NTSC color bleed and scaler used from nearest neighbour to supereagle/hq2x and so on (I think you could safely skip bilinear as I don't think anyone would want their games blurry)
- Easy input config instead of aving to fuss with files like you currently have
- Extension config to set the paths for Intellivoice/GROM/ECS and so on bios files and enable/disable them as needed
- (not necessary, but...) a library where you could scan one or more folders for ROMs. It could then detect game name based on a hash of the rom file, going for the file name in case the game wasn't recognized.
- Rewind function so you can undo a few seconds if you made a mistake.