FDF,
CDG cannot be avoided at all costs, it's a truly awful airport.
I always love airport I can look up at and say 'wow' - and that applies to both terminals at CDG. But airports loved by passengers AND architects are rare. What makes you dislike it so much - at least LYS-CDG-EXT would be within T2 - BE used to use T1.
Put it another way, LHR had become a 4 runway airport back in the day and slot availability was not an issue, would there be a business case for connecting regional UK airports to the main hub, for example, BE feeding BA's long haul routes or WW feeding BD? Would the no-frills big boys have moved in?
Of course there would - it is always natural for carriers to use regional routes to feed their home market. National pride / loyalty / - more likely language for one, and there is latent demand for o&d on these routes too.
But the simple reality is that domestic routes in the UK are under threat from too many angles. Trains get overcrowded because our system allows people to board without reservation - the French would just make all long distance services reservation only - but doing that here would send fares through the roof! Most people will still take standing like cattle for the first hour or so (many trains empty as they head away from London) over all the hassles of domestic flying - train must have about 80% market share by now on MAN-LON?
More likely is that eventually, as HS2 turns into something useful and evolves into HS3 & 4 (if all the optimistic predictions turn true) - then routes like NCL & then EDI & GLA from LHR will become much thinner too.