I've used all the major systems from the 3 'premium' manufacturers. In my view..
The nicest overall system is the Mercedes Benz MBUX (In terms of look and feel and the level of features offered)
The easiest to use and most functionally useful is BMW iDrive (It just works, everything is logical and the various different features are well integrated. Plus the physical controller is far better than the touch screens)
The worst in terms of interface, menu and usability is Audi (Though the digital dashboard side of the Audi system was class leading for years until MBUX came along and even now despite looking a bit dated because of its fairly low resolution is still more useful than the BMW version, even if not as nice looking).
No real experience with the VW system but see little reason why it would differ that much from whatever the system in the current A6 is.
Never experienced the issues you have with iDrive - it just works, and all the settings are in a helpful menu called... settings?
I think wanting to run cooled seats in the rear and heated in the front is a fairly unusual requirement so you can't blame a manufacturer for not thinking of that one.