I mean, you can maybe describe the “feature set” of the prebuilt binary in the variant description and forbid all the other variants… Can’t you?
No doubt, with sufficient effort, we could take something inherently simple and make a complicated and undecipherable version of it.
PS: Maybe “prebuilt_binary” is not the right wording since most of the ports can already be installed as “prebuilt_binary”. Maybe it should be something like “bin_only” ?
IMHO, bikeshedding the variant name doesn't get past the fact that this is not a build variant, it a completely different animal.
K