I can give you a partial answer to your query.
I friend of mine supervises the production of armor kits for trucks and Humvees here in Albany, GA. I can tell you for sure that they ARE working triple shifts and overtime to get the job done—and have been doing so for many months. They are also busy modifying existing designs in response to emerging threats and “customer” suggestions (e.g., increased height to improve head protection).
As for opening new factories: I have gotten the impression that there is some difficulty getting adequate supplies of armor grade steel. Such steel also requires special equipment to cut, shape, and weld, so maybe there is a shortage of facilities with the necessary capabilities. I do not know if Humvee armor incorporates ceramics (e.g. Titanium DiBoride) but, if so, there are relatively few companies capable of producing such materials in suitable sizes and volumes (e.g., Ceradyne Inc.).”