But I totally disagree with the premise of this. Irrespective of limitations on numbers, if we are talking ideal-world wish lists, what we should really be working towards is a system where there are so many talented Brits that the imports are earning their slots and filling the shortfall.
You won't see successful Leagues in NA saying things like 'Let's flood our system with Europeans and the home-growns can earn their spots'.
Plus we do sadly have to remember who we are dealing with here. There are still enough people left who made the brilliant Superleague decisions to have us completely implode once more. Ask Franny what he thinks about unlimited import slots and what it did for his career. It is all very well having Denis Chasse on your team but if Ben Davies would be seen as a liability (just an example) on a roster full of Chasse's then he just won't get the chance to play alongside the 'talent' (another of your points I agree with. It is vital they are integrated into pressure situations or they will never develop).
Personally I think the model the BNL had - 8 Imports - is a sound one for this country. I think it's fair to say our performance last year (as pretty much a BNL side for the whole year) backs that up. Providing you don't do anything like throw away the team that feeds you young talent, of course
You could make a halfway house of throwing 2 or 3 dual-nats at it and reduce that before you do anything else. All this though is dependant on planning, structure, character and those who care for the sport and it's development rather than hanging banners at all costs.
So no breath-holding is advised.