And yup, if they go for it, they'd likely use JAN3's centralised service, which should be way more convenient than storing private keys.
Well, I wrote this in the topic about El Salvador and am writing it here. In this way, you can even introduce moonstone into the payment system, because your assets will be in a centralized wallet, to which the government will have access.
But Bitcoin is designed so that each user stores coins in a non-custodial wallet.