Considering the DoD hires in-house devs, and the intelligence sector is supposed to (whether or not they do is another matter), this doesn’t seem to be a terrible notion. It would also give the NSA incentive to do its real job, that is, standardize the protocols for electronic communication so that they’re robustly secure rather than spying on Americans.
And by making everything obligatory open source, it would fill out a public-domain library of data logistics code.