I think the only way I would get VW to upgrade the infotainment to the latest D variant is if the software issues on 1666 persist, which I presume 1788 resolve.
There are two software tracks:
5H0035816B - the unit without nav in the dash - has software 1662-1670 (so far)
5H0035820D - the unit with nav in the dash - has software 1788-onwards
To resolve your issues you want something newer than 1666 (which I have with no problems other than phone not connecting and the climate sync not staying sticky).... but be careful, 1668 apparently introduces more problems.
BUT any of this infotainment software isn't the only source of gremlins..... there are other systems too - see my OBDeleven dump thread and you'll see them all.
One of the problems on top is a faulty steering wheel that can only be fixed with a new one. If you get travel assist not available, its that causing it.