mess--what mess?
Probably a rhetorical question Fairdeal but I just can't resist taking the bait.
1. How many airports could generate enough traffic to really merit service to LHR which are not currently served? It's a small country especially weighted by population. Surface access is what really matters.
2. If you go for a strategy of full on commercialisation and privatisation as UK did, don't expect a nice neat planned solution like KLM/AMS. Expect shareholders breathing down the neck of BA questioning every marginal activity like Connect out of MAN and BHX. Expect third level routes to be shed to flybe and Eastern who can't obtain slots at the hub and couldn't afford them even if they could get them. That's the market.
3. Market has produced the locos and point to point to an unimagined degree. Look at the places you can go direct from any of the top ten airports. The need for hubbing is that much less. So the opportunity is reduced, not just at LHR, but at CDG and BRU as well.
4. Suppose R3 does eventually get built, I wonder what proportion of the extra capacity will be taken up by regional spoke to hub on a genuinely commercial basis paying their share of the infrastructure costs. Quite a few backs of quite a few envelopes are going to be filled up doing those sums over the next year or so. But I don't think we will ever see the equivalent of United Express or American Eagle serving Plymouth or Inverness out of Heathrow.