There's two sides to this, if it's not a public service, why should it have a certificate from a public CA? If your risk assessment says that you do not need MPIC, then just don't do that, yourself. The second side is that if it's so tedious to approve and install, use solutions that require neither. Surely you don't need to have some artisanal certificate installation process that involves a human if you already adm…
"If it's not a public service, why should it have a certificate from a public CA?" Probably because making sure that clients trust the right set of non-public CAs is currently too much of a pain in the ass. Possibly an underrated investment in the security of the internet would be inventing better solutions to make this process easier, the way Certbot made certificate renewal easier (though it'd be a harder problem a…
I don't see a reason why that should be a problem to solve for public CAs and rest of the internet? Complaining about multi-perspective validation or lifetime is silly if the hindrance is someone's own business needs and requirements.