The lion kingdom started wondering how commodore 64 programs could be seamlessly integrated in a modern desktop.  The mane need is to make the emulator behave like a native windowed program.  It needs a way to trap mouse events when the pointer is over it without having to think about alt-m.  It needs to exit without a prompt & when the program exits.  It needs a way to access files on the host filesystem instead of on a disk image.  It needs to just show an optimized display without all the other widgets or borders. 

It needs to be resizable & have persistent settings like a normal program.  There was once a horrendous CRT emulator for vice, but it still had size limitations.  Arbitrary resizing would most certainly require opengl/vulcan/opencl/CUDA.

 Command line arguments passed to the emulator need to go to the program being run.  Then, conceivably, C64 programs could be indistinguishable from host programs.  They could be wrapped in a .sh file & run just like host programs.  The easiest way might be overwriting the disk image.

There should be a headless mode which just runs a program with access to the host filesystem.  Possibly, it could access a serial port on the host or a /dev file for I/O.  Maybe JSR FFD2 & JSR FFCF could be indirected to the console.

Seamless C64 integration is a key amount of value lions need to do any significant programming for it.  Then, it would be a lot closer to a useful tool to create vintage looking art, play C64 games as if they were native host programs, or running utilities on host files.  It would be stripped down to just the programming model.  The I/O wouldn't be a very accurate replica of the time.  There would be file name translation.  Host filesystem access would be a game changer for just writing file utilities.