How about some kind of visualization/tabular overview of the grammar in Bunpro?
E.g. for each grammar entry the synonyms sections could show this for the displayed grammar point.
The visualization could enable you to compare the formal register and on what kind of words the grammar can be applied to (adjectives, verbs,…) at a glance.
This would allow deepening the understanding of grammar points, especially what is the right context to use them.
Additionally there could be an overview page that groups somewhat connected grammar roughly and links to pages containing the same kind of information as above.
This would be another Unique Selling Point for Bunpro, at least I don’t know any other tool doing hat.
Maybe this could even be based on existing data that is already in your database.