One question to sort out in your mind, up front:

If your husband says no. Absolutely not. No sex with anybody but him, ever, for the rest of your life (or his if he dies first). He is not down with an open marriage...

Will this eat away at you? Will you lay awake at night wondering and fantasizing about other sexual partners? Will you be strongly tempted to cheat? Will you eventually hit a breaking point where you feel like your husband is controlling, insecure, and is depriving you of something that you think you have a right to experience? Will you divorce him?

Will him saying "Hell no" destroy your marriage, or will you just shrug and go on with your normal, monogamous marital sex life?