I am supposing that the idea of moving outside London/beyond the London Underground is not sacrosanct, despite the heavy resistance of supporters, and that the club is willing to risk alienating/losing supporters to safeguard the future of the club.
In this case the catchment area would cover probably anywhere within about an hour's travelling distance from London in all directions - maybe into any of the home counties.
I know this is provocative and am not meaning to be so, just to create a frame of reference.
In theory, there are four realistic 'transaction' scenarios:
1) To purchase land, have an architect design a Stadium and then have it built. Obviously we have no Stadium to sell. We would assume no support from a local council. We would also assume no support from the RFL. Thus this would be 100% funded by David Hughes. This seems to be the least likely scenario. But it is attractive to supporters, with the closer to central London the better.
2) To become the tenant of a club who already has a Stadium and plans to remain there for the foreseeable future. The club would have a stadium which is reasonably close to the RFL requirement. A carefully chosen partner would be someone
without a realistic chance of going into a league which pays so much money that when they return to success that we would be seen as an inconvenience/pitch damager/pitch blocker. This seems to be the most wanted scenario for us, and if our rent is always seen as highly desirable, not peppercorn, then this could be lasting.
3) To form a relationship with a club who has a Stadium now and to share in the expense of building a new Stadium with them, thus creating a legal entitlement to the ground. This would probably mean support from the football club's local council and would require David Hughes to pay in, but not necessarily as much as a half share. This would seem to be the best long-term scenario.
4) To buy the Stadium from a club who is moving out by using a long commercial loan and effectively paying down a mortgage. This would work best by taking over a stadium in a relatively cheap, downmarket area which cannot be instantly transformed into a more luxurious or commercial development. This would be an ok scenario, especially if the Stadium is simply too small rather than being decrepit.
There are of course fantasy/silly scenarios such as sharing with a Premier League club, the Olympic Stadium, Twickenham or Wembley or the RFL offering to build us a Stadium but none are appropriate.
I don't see us evolving a very small ground with no quality Stand into a full Stadium but I'd love us to find someone who genuinely want to work with us, with a supportive council and secure our future, even if it means a little extra effort 13 times a year from me and others to get there.
Cheers
Mark