I think the experiement would be interesting...
But its a good point about the BB tubos with no lag and also the new VTG Turbos on the 997.
However are they really ZERO lag in all gears under all loads? Any charts of a torque curve?
An SC will produce boost at 0 revs...
The cost wouldnt be too extreme if you can do the DIY yourself. There are programmable ECUs out there such as Megasquirt where you can program it yourself. The added weight would be my biggest concern.
I would like to see the boost/torque curves on the BB turbos, if they are that good I would swap them for my two k27s (ex race engine)