Let's make few things clear first of all.
FollowToStop and Stop&Go are types of ACC functionality embedded in the radar as a SWAP code(aka FEC).
Follow To Stop allows to keep ACC activate after performing full stop only for few seconds while Stop&Go supposedly keeps ACC active with no time limit.
To get Autohold functionality on a T6.1, EPB has to be introduced to vehicle CAN-BUS network.
This is quite popular exercise on a PQ35 platform with MK60EC1 ABS by adding 56D EPB controller(the only one as a stand alone unit on PQ platform).
I am not aware of any stand alone MQB EPB controllers (happy to be corrected) so it seems that the only way is to introduce the EPB emulator on the T6.1 CAN-BUS.
I am not even considering ABS retrofit from any other MQB vehicle as I can't see anything being suitable (from the safety perspective).
As an example NAR Golf MK7 is a MQB vehicle and it uses manual parking brake as opposed to the ROW Golf MK7 with EPB.
Some people in America do retrofit EPB by replacing ABS unit and using European version instead.
Summarising, to have the maximum "convenience" experience from OEM VW "AI systems" the following are required: EPB, ABS with AUTOHOLD and STOP&GO ACC.