I agree that 4 MB don't make sense, this is just the vibe I'm getting but I hope I'm wrong
As for Lucia, I honestly would not bring her regardless. She's never playing, and when she does she is deadweight on the front and on the back just ok reception and good defense. If she's not able to have at least a decent level on the front row and just has to play as second libero, I would bring an actual libero instead. I don't know, maybe she's going to be on the VNL and depending on how she performs there she might get a call.