For me, it's about time to rethink the concept of group stages. I'm not so worried about the number of teams, but it would not work with the classical group system.
A mathematician, whose name I don't remember, came up with a great idea some years ago. This made it into 3 pots (with the best team in the best pot, the middle teams in the 2nd and of course the worst in the last one) in a system where everybody competes against everybody. This means 1 match against a team from each pot, and then all teams are in the same rankings. This would mean that every single match is important, and every goal the same. Then it could still be with 24 teams without a lot of boring matches, and it could still be possible with the same amount of knock-out matches.