Introducing any outside actors at all objectively diminishes the security of the whole model by becoming another link in the chain, even if that link isn't necessarily the weakest (and I certainly believe it would be, because both DNSSEC and the public Certificate Authority industry are object lessons for the abject failure of highly centralized global, government-wide, or even just company-wide security), but simply increasing any of the surface area is enough to decrease the security of the system.