4.) A special loop command (like Uxx or something) where U00 sets the loop start point and Uxx sets the end point and number of times to loop.

Hi and thanks for your suggestions, I'll consider these. Changing Gxx might be a bit tricky due to the way it works now, but I'll look into it.

The home-key behaviour is copied from Impulse tracker, so maybe that should only be used when the impulse tracker mode is enabled. I didn't think of that.