15+38+6= around 60 matches at total, League, cup and CL. That shouldn't be a problem for players earning millions of dollars per year, and these squads usually have 20 players at least, rotating them in all the competitions would make 40 players at max for players, not a big deal if you ask me.
Like Bozi said it mostly benefits the rich clubs out there, but also I don't want shitty teams get involved in CL "For the sake of football", but yeah, 4 teams from a league is a joke, 2 was good, but 3 is better, Arsenal, Man.utd, Chlesea, Juve, Milan, Inter, Barcelona, Real, Sevilla/Valencia, this looks better imo, I mean stronger competition. I miss the days of 24 teams, I think that was the perfect one, I am not sure about Platini's two-leg competition style.