I don't ever see a day where you have a system like in the U.S. (and Australia for that matter) of drafts, spending caps etc. It's too far gone and the big clubs in Europe would object vociferously. I think if it came to it, they would break away and make their own league.
Having said that, UEFA has implemented the Financial Fair Play system but it's still a bit of a joke. It's too little too late. There were always big clubs (e.g. Barcelona, Real Madrid, Bayer, Man Utd, Liverpool, Milan, Inter, Juve etc.) but the disparity now is ... just so large it's become ridiculous. This is because of the CL and the huge prize money. It started the snowball effect and has just rolled on.
But I don't know what you can really do about it. Maybe UEFA could halve the prizemoney and instead give it clubs directly, even those not competing in Europe. Hmm, now I'm sounding like a commie.
You want to know what I think is the best way to stop the massive disparity ? Go back to the old days, maybe tweaked a little.
1) Only allow 5 foreigners in the squad. Back in the day it was 3 but I think that's maybe a bit low.
2) Don't allow a club to have more than "x" number of players in total. This is to stop clubs buying 60 players and loaning them out. If you have a player, he should be in your squad. Otherwise, you need to sell him.
The beauty of point 1) above is that it curtails the spending power of all "big" clubs. Yes, they'll still get the best, but they won't get "the rest" who are just a little behind in quality, and these players would be at different clubs. You wouldn't get the concentration and stock piling like you have today.
And you'd actually get to see teams in Europe that are composed of players that are local. Now, if you beat Arsenal what did you beat ? An English team ? I don't even know what the heck it means anymore.