I'm in the same boat as Lippo here; not much needs to change. Small tweaks if you think it can be improved but don't change things for the sake of change.
The current format is very popular and it seems to be working well so keep it going
The qualification play offs is a great idea to keep the 16-team group stage while still allowing more to compete in the early stages. Though I would say let people choose their own teams as certain teams suit certain style. I can't play with Real Madrid for example; the way I play football just doesn't suit them.
I think the automatic qualification for reaching the semi-finals is important to make people feel like their being rewarded for getting far. Being a finalist yet still having to do a qualifier to get into the groups feels like it's there just for upsets.