What does your W want? Does she like working? Has she always wanted to be a SAHM? If she isn't really interested in being a SAHM, she may not be happy in that role. If she is unhappy, your SL isn't going to improve. She might be happier getting a different job that doesn't consume so much of her time.
I don't like the job description idea. You are partners in your family and in your household. It just wouldn't sit well with me to receive it, even if it were done in a lighthearted way. I'm sure she could craft one for you, too... How would it feel to receive that?
The most important thing, I think, is to first be sure that she is enthusiastic about being a SAHM.
