This will almost certainly never get implemented because the community has a more or less accepted workaround. Run more than 1 pi-hole.

It's a common-ish practice in the community to have a restrictive pi-hole running in your guest/kids network and a more permissive pi-hole running in the trusted/adults network. Pi-holes require so few resources and maintenance that it's not much burden to run more than one.

It would be a pretty large feature to support separate blocklists per IP range.