That's cool. Here's a question, though: What if you DON'T hatch a Pewter? Then what? Do you get anything? Or, conversely, what if you hatch out MORE than one - and they are of different sexes - who gets the male and who gets the female?
I can understand having a simple breeding exchange. There is nothing wrong with that as long as everyone knows all of the terms going into it. Don't be dissuaded by everyone telling you it "can't" work, "won't" work or that it will destroy or fragment your relationship. As long as everyone knows EXACTLY what is expected of them from the beginning and how any of the results are going to be split (whether through sales, trades or whatever) then you shouldn't have any problems.
Figure out how you will handle the above questions and also take into account:
Feeding costs
Possible Vet costs
Bedding costs
Incubation costs
Possible Death - is he reimbursed if she dies in your care? This will probably lead back into the "Vet costs" category
Get all of this in writing between the two of you and as you are going over and thinking through these main points most of the rest of the details will come to you.
Just remember to take into account all of the things you KNOW will happen (she will need to be fed, she will need bedding, etc) then consider as many POSSIBLE scenarios as you can come up with. Consider the best case scenarios (a large clutch comprised of only Pewters) as well as the worst case scenarios (his female dies, gives your animals mites or some other infectious disease, the vet bills mount, and all of the eggs that were laid were infertile or only hatched out male normals) -
Some (or most) of the "bad" things that could happen are listed above but there is more to consider -
What if she becomes egg-bound?
I'm sure there are more things to consider, but you are starting to get the idea.
Good luck. Feel free to email me and I'll be glad to look over whatever you type up to see if you have missed anything (just nice to have an extra pair of eyes look things over sometimes).
-----
.
.
.
.
Stay United!

I'm still not sure if it's weird that my best friend is a two year old boa named Ronin. He's quiet, non-judgemental and listens... what more could you want?