With my fleet we enjoy roleplaying missions and giving them our own story spin through in character dialog.
Now since Cryptic's number of missions is limited we are in need of foundry content to keep this going.

Who can recommend missions that are light enough on dialog to allow the RP some breathing room, are playable by groups and still make sense, and are not so era specific that they only work in 2409+?

I can't really recommend created foundry missions. As it is one aspect of the game that has yet to grab my attention. However have you not thought about creating your own foundry missions. Look on YouTube for some tutorial guides and best of luck!