I can't remember any concrete reason right now as to why it was introduced. Removing it may be difficult, as people definitely are using it.

I understand you are reworking this for your own use case which sounds quite complex and large-scale, but keep in mind that most people use the ACME module for the simplest of cases - they have a vhost, they set enableACME = true, and they magically have certs. Making the ACME module work for as many use cases as possible is important to reduce fragmentation in the community, but there is a limit.

I definitely think there is a solution here where we can keep the self signed cert optionality and what you are trying to do. Your primary concern seems to be around the lack of a syntactically valid cert being present for consumer services. If this option is explicitly set to false, then it can be assumed that users do not care about this guarantee.