Well I wouldn't pay for it to be idle; if you want to ensure you have the ability to do it, then you buy some proportion of it's potential output at their increased costs; but while that's happening you work on all the reasons it's more expensive.

The logical thing is that the government buys them continually at the higher price which justifies the existence of the factory with the requirement that it is made here and if this is not sufficient motivation you make buying something more buying something profitable contingent