What else would be a pain in this project?
One thing that comes to mind, is speed signal differences.
For example, if you have much different size of wheels (compared to wheels in car that gearbox comes from), DSG will not be happy about it because it measures speed of all the axles in it. If CAN reported speed differs too much, there might be odd behaviour.
On the other hand, if you do not send speed information to DSG at all, it still works suprisingly well.
This is the case in my car, '86 Scirocco in which i have installed a DSG7 from Golf 6.