[Answer]-Django cms: template for placeholder

You can limit plugins allowed in a placeholder using CMS_PLACEHOLDER_CONF

See http://django-cms.readthedocs.org/en/latest/reference/configuration.html#cms-placeholder-conf

Update:

I read your question again, if I understand it correctly.. you are struggling with wrapping plugin with html class?

Have you had a look at https://github.com/divio/djangocms-style

It would allow you wrap your existing plugin in whatever classes you need 🙂