That's really useful info dd. Sorry for misleading you digitalhippie
No worries, we're all learning... part of what we call life
All you must do is make sure to first adapt the cluster to the ecu, not the ecu to the cluster. The only time you have to worry about not being able to reuse the RFID transponders is if you don't have any of the original files.
As you have both the ecu AND the cluster, this is very easy. The only shitty part is like you said, there will be some games involved due to the incorrect flash being loaded onto the ecu currently.
BUT, it'll be fun-lol.
It'll be a learning experience. But I'm good to go w/o bootmode? I ask because I've seen other threads stating that you can't flash the ecu with immo enabled... so I'm afraid that once I flash the stock allroad bin and enable immo again, I will be unable to flash back a new bin (or the current screwy bin) w/o bootmode