You joke but a lot of suppliers to the US government, including the military, works on a two-contract basis - the initial acquisition of the item, and then the support contract for the item.
A lot of suppliers bid low on the initial acquisition contract, because they know they can make up losses on the support side later on. The supplier is also more willing to take on more risk as part of the supply, again because they can make money back on the support.
If the support contract becomes uncertain because the military can go elsewhere to support the item, then expect the supply contracts to get a lot more expensive, and a lot fewer contractors willing to undertake fixed price deliveries for anything.
The US government did try something similar to this in the late 1980s and early 1990s - they split the procurement of new items into two contracts, the first being the development of the item, and the second being the delivery of the item. Whomever won the development contract had to hand over everything needed to produce the item to whomever won the delivery contract. The problem is, all the risk exists in the development contract, and all the profit exists in the delivery contract.
It did not go well and after a couple of very bad outcomes for development contract winners, they stopped bidding. So the approach was dropped.