I was kind-of wondering how you managed the early builds, too. I come from the computer world, but we had similar prototype, pre-production, early production and final production phases, each very different from the others, but our mechanical process was quite similar to yours, even though the production volumes were higher.
We found that we had to be careful ramping our supplier shops to maintain quality and delivery times as we dramatically ramped up from prototype to production volumes. Some smaller shops don't want to go beyond a certain volume so we developed several suppliers for much of the product and shared fab info between them. That way, we didn't kill any mom and pop shops and could throw bonuses at them for speedy delivery or for working with the larger production shops.
I'll admit, that we burned our share of smaller shops with too-short turn-around times or ramping their volumes too fast, but we learned how to manage a wider field of suppliers while keeping them all happy. It's a shared learning process, for sure.
And Happy Holidays, Carey!