Two plot ideas that might have been fun
1. Sam gets a part time job during the day while the kids are in school. Endora is disgusted and wreaks mischief.
2. After yet another witch vs. mortal debate between Darren and Endora, Sam challenges Darren and Endora that for a week, she tries mortal life and he tries magic life. I know these ideas were explored in the dodo bird episode where Endora lost her powers, and in fact a couple with Darren - but in this case, the two of them try to "top" the other's progress at his/her attempts at a different lifestyle. All the while, each of them are making a mess of things.