There must be more renderings of 'Norm island' to analyse re: just what is at the end of the runways, and what is between them.
HKG is great engineering, and great architecture, but it came at a massive price, in a city that didn't have other greenfield sites to continue, and that really did have a dangerous approach.
I'm not sure how much 'not now Darling' was relevant re: Cliffe and Rugby, both came from private consultants, and he won't have got a look in - iirc, the report pre-dated his tenure in the transport job anyway, which only seems to be a staging post to other positions these days.
The cost of the Foster proposals has been put at upto £50bn (+where do you go from here), Boris Island not much less. Rugby was far cheaper at c. £6bn, and it too was close to high speed rail lines (forget about TGVs through Crossrail, that really is a non-starter, fast and slow don't mix).
However, when I saw the RUG plans, and the then loyal poodle MPs bark out their cries against them, it was obvious that the government wasn't serious. you only had to ask any airline if they wanted to move from Heathrow to the middle of Warwickshire, and the answer was obvious.
So we're back to making the best of LHR - who says air travel is going to grow anyway, there are plenty of reasons (fuel, tax, CO2, high speed trains) why demand may well stagnate at best, and quite possibly shrink. Let LHR take the transfer pax, and allow limited expansion at STN, LTN, and to a lesser extent (given current usage of single runway) LGW. Oh, and overflow to SEN, then MSE................
London has enough airports!
PS - re: birdstrike, plenty of interesting developments in this field, by time this airport did get off the estuary bed, engine technology should have advanced to being able to cope with this problem.