Whilst I agree with much of this there are some pretty big pitfalls when it comes to quoting numbers.
All this tuning will be done with the engine in the car so either on a rolling road or hub dyno with all those hard to determine losses and correction factors in the mix. Additionally this V6 engine is knock limited so if the cooling in the dyno cell isn't up to snuff (and most aren't for a 400bhp+ car) the ECU could pull 30-40bhp giving a wildly deflated number. On top of this there will be natural variance from car to car... I tested two side by side and there was a 5bhp difference.
So when I get asked what the TVS1900 kit makes I say as it is; it will do about 350bhp @ the hubs an TDI south hub dyno in Thurrock. We don't know the exact losses but that hub figure would equate to about the 400bhp mark. Those figures are very repeatable run after run and i know the dyno itself is repeatable from the many years I've used it and the many different cars which have been tested by it trackside.
Clutches and gearboxes, from what I've seen, aren't such a stumbling block as people make them out to be. For track work its wise to fit a gearbox cooler and that's true whether the engine is upgraded on not.
We don't send the ECU away, we just re-flash it. The nice thing with this approach is that you retain the stock drivability. You're right, there is some low hanging fruit to be had in terms of tuning but the beauty of the TVS1900 is its simplicity, and its robust. Charge cooled kits are on the way but its a much more involved install so more £££... you pays your money...