It may be sufficient to add an option Use on homepage only beneath the default META fields. This at least would solve the problem with duplicate META entries.
Though the user would be forced to always enter META description/keywords for any entity, as no fallback would exist anymore. But it's OK, this is something he should do anyway to enhance his SEO ranking.
Migrated from CodePlex: Issue #211 from muratcakir, on 12/10/2013 11:05:40 PM