OK, so we've got Lucien and Phaedra. But you wanted something with Keiran, Frank or Barnaby. Since you aren't using Ella so much right now, let me see...
Well, I think the deal with Barnaby is that he considers Frank his best mate, but Frank obviously doesn't. He's trying to look after Mai and going on all of these secret jobs and, frankly (hah) he can be a bit of a butt. We already knew that, though. So something I'd like for Barnaby is for him to find someone who actually considers him worth their time. That, or somebody who'll see Frank treat him badly or whatever one day and be like "no way, man. Not cool" and either tell Frank off or decide to help Barnaby himself.
Since Keiran/Phadra feels aren't really a thing anymore, we could do something with him being conflicted about Kenna and her catching on..? I don't know. I can't see an instance when that would happen unless she stopped by the shop. He'll be there more during the summer so the boys will all be in the same area fairly often, along with the kiddos.
Otherwise, I don't know what to suggest.