I get it worked
On the end the best was for me the RAM upgrade solution.
I upgraded to 32gb RAM. The intersting thing: even I have so far now nearly 100 hundred Kontakt orchestra instances (as a test), it needs “only” 20-22gb RAM. So always enough in reserve (for more).
So I added so far also a lot of Omnisphere, Zebra, Nexus patches. Everything is preloaded. Great!
And, I had not to rework my Kontakt multies.
Also great: all the instances of the VSTi preloads quite fast.
Off topic: I always working now only with linked racks and states (beside song). This is really great!
I made racks for single VSTi with the best of presets behind (by genre). Now I can/could combine each VSTi/preset with other VSTi/presets and everything is preloaded. So, with C3 have now such much more opportunities and get them work out very fast.
C3 is really a great or the best DAW