the proposed legislation must not make a criminal out of anyone who's currently a law abiding individual in compliance with all laws, who does nothing differently after the law passes
Wouldn't any new law about firearm sale, ownership, or use do this by definition? If it doesn't change any legal things into illegal things, it isn't doing anything at all. What kind of law can you imagine that would pass this part of your test?
With some industry software, the proprietary stuff really is better. There are plenty of great FOSS tools out there, but not always the exact thing you need. For example, PDF software: I don't know of any editor as powerful as Acrobat. And I absolutely hate Acrobat, but it's the best tool out there for modifying a PDF.