The only thing that I see as a potential problem is the veto thing. An initial veto power, as in "Please don't start dating her, she skeeves me out," can be a great idea. But if your wife is expecting that she can say at the 6 month mark "Actually this is bothering me more than I thought, I'm calling in the veto, you have to stop seeing her," that could really mess up all the relationships involved.
If you refuse, you'll be breaking your agreement with her. If you comply and find yourself broken-hearted, you could end up being resentful in a way that's very damaging to your marriage.
Much better, in my opinion, to leave it up to a matter of discussion. You can say "You know you're my first priority and if a particular outside relationship or poly in general was endangering our marriage in a way we couldn't resolve I fully believe I would end it to keep us together," and that's subtly but importantly different from "You have the right to end my outside relationships whenever you choose."
Otherwise, looks great! For helpful basic do's and don't's, have a read through some of the beginner's resources at www.morethantwo.com
. Good luck!