Elira would legitimately be a huge boon for Cover, because of all her connections and stuff. But you could do without her honestly, she's in deep with the Ethyria girls, and she's basically just a JRPG endurance streamer anyway. Rosemi is someone seiso enough for hololive, if you think she's good enough. I don't know, maybe she has a Mumei type appeal, I could never get into cute vtuber very much.
I would love to see Pomu in hololive, I think that's right where she belongs. That is, if HoloEN could get their management issues sorted out, they're clearly having some behind the scenes problems.