28 cars on a grid shouldn't be a problem
Add a 4th qual session
1st - loss 4
2nd - loss another 4
3rd loss 10
4th final grid 10
I think it would be chaos at some tracks first corners

---------- Post added at 21:10 ---------- Previous post was at 21:08 ----------
new pit lane for Monaco is being planned, may have to increase that.
http://www.f1technical.net/articles/59