I don't know about this setup in particular, but a bi-turbo installation has been done a few times; either by modifying a PT/ABH, or by installing a setup from another model. Details I don't have, but there seems to be plenty of room to accommodate.

How well the original auto box can deal with the performance is of interest to me. I am running a chipped and quite lively 3.6 setup, and no complaints. But I'm unlikely to be over 300hp peak. I want to supercharge one of my cars, though.

85 WR quattro
90 V8 Silver, 91 V8 Black, 93 V8 Lago
93 100e quattro V6. Titan, i think