The 5 top leagues are pushing for it and they have the bigger pull
So, by my reckoning that's:
Man Utd, Chelsea, Arsenal, Liverpool, Man City, Tottenham, Lyon, Bordeaux, Marseille, PSG, Bayern, Schalke, Borussia Dortmund, Werder Bremen, Stuttgart, Inter, AC Milan, Roma, Juventus, Real Madrid, Barcelona, Atletico, Sevilla, Valencia.
If I've counted correctly that's 23. So 9 places to fill. And I've assumed those 23 as they're the ordinary members of ECA from the big 5 leagues.
Could work. Not that diferent from CL, but the big clubs guaranteed annual entry and on a weekend.
Or two divisions of 16. That'd be an intense debate selecting the top 16!
I guess another sticking block would be what to do with those extra 9 places left, more to the big 5 (there's already some dodgy teams from France and Germany, but e.g. no Napoli) or would we see the likes of Holland / Portugal / Russia etc getting a team or two in? Surely Ajax and Porto would have to be there.
Notwithstanding how the national associations feel about it. I suspect it is the big teams from the big 5 leagues making the push, and not the league associations themselves.