I'd be fitting everything you can out of the front cut. Immobilisers can be defeated if need be....... Leave that BOV idea, as an idea and go with a new diverter valve. You could probably make the Climate Control work but you need all the diagrams for both systems. I am thinking too hard basket.
This has been done a couple of times on VWWatercooled. Stan did it and there's one just gone to Camden GTI IIRC.