It’s about damn time that we should be able to get intermediate signing certs that are domain limited from a public ca and issue out own “real” certs. This is fully supported in the standards. Anyone offering this product affordably yet?
Should the CAs issue intermediate certs that are only secure if a client implements an optional feature?
And even if most web browsers support name constraints properly - who knows if that cheap network webcam does, or that old mail client, or that 20 year old retro PC game?
If you want to uphold the name constraints in your CA cert, mark the field as critical. At that point clients that don’t understand them should fail validation of the CA cert.
Just like you presumably already wouldn't issue LE certs when you need to support clients with ancient CA bundles.
How do you think TLSv1.3 ever got rolled out?
Edit: has been fixed in osx 10.13.3. Idk about iOS.
Security-wise it shouldn't be any worse than wildcard certificates which are already a thing. It would actually improve things, because the user can now issue downstream certificates much more granularly without having to interact with the root CA (so you can issue fully offline for an intranet, or issue extremely-short-lived certificates that would otherwise run afoul of root CA's rate-limits).
They're selling something with a marginal cost of zero for $50 each. A wildcard certificate costs more not because it is materially different or "harder" to issue, but because it replaces many $50 certificates. Thus, it "must" cost more, or everybody would just use wildcard certificates everywhere and reduce profits at the large public CAs.
It is actually possible to get a domain-specific CA like the one you're thinking of. I saw one at a large department of education. It allowed unlimited issuance of certificates such as HTTPS, mail-signing, document-signing, and some other types that could be locked to a DNS domain. However, there was still a cost per certificate and the up-front cost was huge, something like $100K.
I get the negativity towards public CAs, but much of what you said isn't quite right, either.