I agree with you two, I find the big plots good too.

Here's a few ideas I've had, I was thinking it would be cool to get everyone involved in a plot, so how about some sort of outbreak happens in the school, everyone starts getting some sort of illness and no one knows why it is spreading.

Also I was thinking that the flood was kind of good, but I was thinking a few days ago what would happen if the magic spell that stops Muggles seeing the place disappears and a few muggles accidently see the place and before more people see it, everyone has to try and find out what's gone wrong.

And the last for now, I was thinking how about the bludgers go crazy and start smashing up the place, that and all the house elves disappear and then there's more mayhem, like lessons getting disturbed and so on and everyone has to try and figure out why this is happening.