You almost got it with "render individual patch mixdowns"
For the violins in Standard version:
I need ~70 GB of storage for 5 (in reality 4) Mic Positions. This means 1 Mic Position has around 15 GB.
If i now make my own "Mixdown" exactly as I want it I will require additional 15 GB of storage space (as you wrote)
However what I could do now is to put the original 70GB ona a slow and cheap harddrive and only take my personal mixdown on my SDD.
This might not be the perfect way to go if you want to alter the mix in every track you do, but as my approch is "make it nice once and then use it forever" it would grant me 55GB for 5 Instruments --> 250 GB overall SDD space
I second that.
Like timestrech in the "old" vipro, there should be a render button, which freezes the mic positions to your current setup. Disk space is much more cheaper than RAM