Well, I don't have any kind of experience with that 4B module (I think remember iichel did some testing with this module on his vw cars).
I guess you should unmount it and remove it from the GW install list to avoid conflicts with the new buttons of the new MFSW.
I'm also assuming you need to provide a new power supply (+15) and a new communication/wire LIN (doors LIN, T73b/17) to the new buttons, also the ground/earth obviously. This process is explained here in the forum for VW POLO 6R (BCM PQ25).
Once this is done, the BCM will recognize the new multifunction buttons as a subsystem (J453, MFL), which must be coded according to equipment (post an autoscan).
From (4B E440, CAN lines)...
To (J453, LIN) ...