Mike,
Pretty much exactly the answer I expected to the original question (though not necessarily from you,
).
Whilst I agree with both points - neither will work on their own.
Of course, every light piston aircraft can rotate before the rotation point of the Hawker/G 5/Lear/Beech 1900 - but I doubt that any one of them can OUTCLIMB the previous high performance aircraft - so the only way out has to be the low/slow/noisy turn off the centreline.
With regards to asking for the delay - that is exactly what caused the original question - I've witnessed it personally at three USA airfields (Naples, Florida; Vero Beach, Florida; Scottsdale, Arizona) and on every occassion (now six times in three years) when students and/or flight test candidates ask for a delay for vortex, ATC have come back at them with a growl, pointed out that they are classed as being at the end of the runway, and have caused substantial delays by letting other HP aircraft before them.
I truly do not see a genuine approach to wake vortex separation on behalf of ATC.
When I used to fly at Manchester (U.K.) it was very common that a light aircraft would be given an intersection departure whilst an airliner was being given a full length "line up and wait, light aircraft departing ahead for wake vortex seperation" clearance.
We still did an early turn when conditions allowed (to let the guy out behind us) - but this was over unpopulated territory that would not write to the airport to complain about noise.
I agree with all your comments, Mike, good text book stuff - but they won't work.