Thank you for your efforts, Eric. Not the answer I wanted to hear, but sort of expected.
I did not look forward to transferring all important data to the new user account, so I thought I'd use the fast-switching idea, and just log-on to use Logic. Started with this idea and was confronted with alerts to re-register software and NI libraries.......
So, I'm sticking with 10.1.1 on my usual user/account. Maybe there will be a 10.2.1 in the near future that addresses my rare (but not unique) problem. Maybe somebody at Apple will look at my two dozen crash reports and tell me what is wrong. Maybe when I can get to my Disc Warrior stuff (I'm in temporary digs till I move in November) I can get a more thorough permission repair done.
No complaints with 10.1.1 - just disappointed I can't get at the new stuff.
iMac 3.4 GHz i5, 24 gig ram, OS 10.14.6 (Mojave) RME FF800
Omnisphere, Trilian, RMX, Sup.Drummer