Walt may be a genius at solving problems, but he has no common sense whatsoever.
How are you going to explain how you got so much money to your family and friends? Laundering 5 mill properly could take years. Get out of the meth business, take like 1 mill and launder that. Get your Teaching job back or talk to the people at Gray Matter to see if you could get that back.
Then, tell skyler your done with Meth, get family back (worse comes to worse you get a divorce? Big whoop your rich). No one figures out it was you, become friends with Pinkman, No blue Meth on the market.
Only one stopping Walter from becoming Rich is himself.