Let's see:
1. Eliminate all non-cartoon programming from the air. Sorry, but I don't find any of it funny.
2. Give Nick Jr. its own network, which would free up considerable time from the schedule.
3. Bring back some of the old classics, like Rocko, Ren & Stimpy, Angry Beavers, etc. and put it into the slot that was once occupied by Nick Jr.
4. Keep most of the afternoon, evening schedule as is.
5. (and most important) DEVELOP SOME NEW CARTOONS!!! Sorry, but SpongeBob isn't going to be around forever, and Nick will need another flagship cartoon once SpongeBob's time is up. And currently, they don't have one.
6. (this is a maybe) Ditch the current format of Nick at Nite (rerunning old sitcoms) in favor of creating programming like the stuff on Adult Swim.