You don't have access to the cache instances in 2LC, so your idea of adding a cache listener won't work.
I think the easiest is either:
- Have database replication or have a single database rather than 2 separate databases, in which case 2LC would work just fine without any tweaks.
- Or don't use 2LC and instead have your caching layer that behaves in the way you want where you can add your cache listeners...etc.