https://lists.launchpad.net/kicad-developers/msg40087.html
The idea is that when the package split then finally happens, we can use
these GUIDs for the separate parts, so users can go back from a split
nightly to a 5.1.1 release just by installing over the nightly, and it will
install cleanly without file conflicts.
Looks like something similar to what you have in mind is already in the works.
More importantly, is that 5.1.2 should be released in the next couple of weeks; likely fixing the crashes you have experienced.
The Version 5 releases seem to have been buggier than before, but that could simply be due to the increased number of new users using the more advanced features.
Earlier there was a great thread about how well KiCad now behaves overall:
I would not hesitate to recommend KiCad for most design work. I really look forward to the future of KiCad in the workplace.