You need someone who knows (!) or someone with the wiring diagrams. On the C5 A6 it can be done without any MFSW controller _ I do not know what the situation is with th A3, perhaps someone will enlighten both of us?
On the A3, the tip is part of the SCSM just like the multifunction buttons. Your SCSM may already be capable of relaying the tip commands, but without knowing your part number it would be just a guess. In the B6/B7 the SCSM is good if the car also has cruise control.
I've just checked, I have the same control module as the owner who retro'd MFSW on his car. 8P0 953 549 F.
I hope I have the correct S/C ring alreadythen too, but I assume so beacuse according to ETKA there's only one S/C to be used for this module. So I guess all I need is a steering wheel with the proper airbag harness!