I think we have seen enough over the last decade to confidently say that only 4-5 leagues would even come up in discussion; that is England, Spain, Italy and Germany with possibly France as an afterthought. Remember, this is a breakaway league, it doesn't have to be all inclusive and would be serving the interests of those involved at top level discussion. Co-efficients wouldn't even come into it in my opinion, as it would largely be based on prestige and the size of the names involved.
Runninng with that, I think the 'must-haves' (that is, teams with the commercial draw to make the league a success) breakdown is two from Spain, four from england (maybe even three), two from Germany and three from Italy; that totals eleven teams. You then have nine spots to fill (in a 20 team league, could be more) where you can invite, for instance, your Ajax and your Marseilles etc. And that's without even considering a second division.
