v4 didn't allow dynamic IDs on invoke but I don't see a reason why we shouldn't allow this in v5. spawnChild already supports this and both use the same implementation under the hood.

Awesome, thank you. Dynamic id's are just what I needed!

This turned out to be slightly more complicated than I anticipated since we were relying on those particular IDs to be static. This bit of the implementation is funky - so perhaps this will force us to rethink what we are doing there in terms of how we allow for entry sendTo actions targeting invoked actors to be "retried".