Yes, we should reduce corruption and break up existing entrenched players, but the core issue is in the structure of that kind of arrangement. I do also think that there's no good reason to have a "corporate veil" in the first place, but that's a broader problem
But that's just a mechanism for the corruption. The contract for the design of something and its manufacture and maintenance should each be separate bids. Even each stage of the design should be a separate contract that could go to someone else. The government says "we need a design for a ship" and they put it out to firms who submit their proposals and then the government picks one and buys it outright. Then they say "we need a design for a propulsion system for this ship" and take bids again. If you need to modify the ship's design some to facilitate it, that's fine, because none have been built yet and the necessary change gets incorporated into the design before you put out contracts to build any of it.
What you want is for each of the contracts to be as small as practicable, to maximize the number of potential bidders. None of this "single contract to design and build an entire fleet of ships and maintain them for 30 years" nonsense.
Claims that you can increase the efficiency of a system by reducing competition should be met with the same level of skepticism as claims that you can violate of the second law of thermodynamics.
But let's try one that should get their ears to perk up. Monopoly suppliers are systemic risk, which is a threat to national security.
In principle this is supposed to be a competitive bidding process, and then the winner is chosen by the most competitive bid rather than the government. In practice the process is corrupt and regulatory barriers are created to prevent smaller companies from submitting bids or project requirements are set such that only one company can satisfy them.
The problem here is corruption, which has nothing to do with whether the corrupting entity is a corporation. Public sector unions lobby for the same kind of labor-inefficient practices because they know that more jobs give them more members which give them more power, even (or especially) when the jobs are unnecessary or inefficient.
The advantage that existed pre-WWII is that neither large government contractors nor large public sector unions already existed in order to lobby for corrupt practices and their continued existence, so the government could just pay someone to do work and then have them to return to the private sector when the work is done. But WWII created such a large apparatus dependent on taxpayer revenue that it had enough lobbying power to sustain its continued existence, and now it needs to be disassembled before we can have nice things again.
But probably the best way to do it is under anti-corruption. You still want roads and ships to be built, but if you could get the corruption out of the bidding process then they'd be built by smaller and less consolidated companies with less individual lobbying power, and then you could address efficiency issues without having to fight a multi-billion dollar corporation or huge public sector union because that inefficiency is their profit margin/job. Another possibility would be anti-trust -- break the big government contractors up.