comp80

I am looking to build a Factory Five 818, and have been presented with an opportunity to purchase a 3.0TFSI (CAKA) engine, 7sp S-Tronic (0B5, sans mechatronic unit), ECU, loom, gauge cluster and key. All of these are from a crashed 2010 S4 with 3000 miles on the clock (yes, really that low)

Now I am under no illusions on how complicated these engines are (have read through the technical manual, and am a mechanical engineer myself), and actually own the exact same car ('09 S4 Avant) as a daily driver.

IF I was to proceed with the purchase, I have a few questions if anyone is willing or able to help.
1) Would the engine, ECU, loom, gauge cluster and key be enough to get it going? Would I need any additional body modules? Perhaps the TCU?
2) If I was to adapt a different transmission (thinking Subaru STI 6 speed) would the ECU have a problem?
3) If I can source a new mechatronics unit to use the transmission, is there any infor out there on removing the centre differential and converting to 2WD? Possibly a question for a different part of the forum.

Trying to avoid custom ECU ($$$) if at all possible. I have RossTech VCDS cable if that helps.

Thanks in advance.