I don't have a problem with watering down the group stages with 24 teams - sides like Belgium, Turkey, Switzerland, Serbia, Slovenia, Slovakia, Montenegro, etc can hold their own.
I do have a major issue with what happens to the round of 16 ...... you will have 4 of the 6 3rd place side make it to the KO round, and that's always annoyed the hell out of me from old WC's. It's just so awkward and also creates an unfair playing field as the groups that play their last game later get more information on what they might need to make it as a 3rd place qualifier.