in case someone cannot wait (like me) and would like to have some ideas, I just backported the current wip declarative Gradle plugins on the 8.7, using some custom simple validation through a plain parsing of the build script file
here, "declarative" for the plugins, "declarative-playground" for the tests (I just ported java/kotlin library/application)
It's a much simpler logic and requires at least an applied plugin, but it features the IDE support
it may be a feasible compromise in the meanwhile