I think life would be a lot easier for you and authors if you guys could toss a bunch of prefab characters into the Foundry contact costumes (ie. Worf, S1 Worf, assorted Klingons, etc.) and then took the more clear stance of, "Don't remake characters seen onscreen in the IP unless we provide you with one."

Maybe have a special naming convention.

Like:

"Canon - Worf - 2409"

That might mess with my Picard mission (where I tried to hide it from looking like Patrick Stewart) but it would be clearer.

Then again, to make it explicit, you could add:

"Canon - Picard - 2409" and just have it be a male in an EV suit. And "Canon - Picard - TNG Era" as a generic male in a First Contact EV suit.

There ya go. If all uses of characters from the shows have to be from a Cryptic-approved costume list, all you do then is supply generic EV suits with the name attached. So authors know, "Okay. I can use Worf but he has to be wearing a Cryptic approved costume. I can use Picard but the only approved costumes have him in EV suits."