For the vast majority of registrars you would find it hard to find one that do not offer DNS. For defunct registrars it does get more tricky but you can have be

For the vast majority of registrars you would find it hard to find one that do not offer DNS. For defunct registrars it does get more tricky but you can have better security than what is provided here. Have the customer first create an account and link the domain to the account and then change NS rather than the other way around. This solves the issue of people discovering domains that point to DO but has no linked account. Defunct registrars is a interesting problem. If they don't have functional name servers then it is also very likely that they don't have a functional portal and customer support in order to change the NS records. Defunct registrars are thus a pretty manual problem, so sacrificing security for easier process seems like a bad deal. A best practice should make the common case easy but secure, and the uncommon case secure and possible.