I have been thinking, who would be the next waitress? Surely not Liz or Ally, no way it would be Rachel, so Annabelle, but how would that even work? Everything would get broken.
I've been thinking about it, and we've got a few candidates.
Rachel - Probably most likely if/when she gets a redemption, but I don't think that'll be soon so I would guess she'll assume a position after the next one is filled.
Annabelle - Possible, but I don't know enough about her or her family situation to decide if being a waitress would be something she could handle in regards to society. Cosy did mention that her promotion to main LI was a timing thing, so that's why she gets 2nd best odds in my opinion.
Elizabeth - If she thought being a waitress for MC would hurt her mom/brother then I could see this being a real possibility. I honestly think she would see the benefit. It'd be a good way to bring Elizabeth into the MC and the other LI's orbit as well, which so far hasn't happened.
Catherine - I'm putting her last, as I think the MC is quite happy having her as his personal princess dishwasher, BUT it would also make the most sense for her to move positions into a waitress as she's already familiar with the whole dynamic. I also think this would allow Rachel to move into dishwasher mode.
Unknown Childhood Friend - For completionist sake I'm putting her down here, as I could see a scenario where she shows up, needs a place to stay/money and is immediately brought in as a waitress though not specifically as a LI, but I'm not putting much stake into this theory.
Alison, Misaki, and Akari I don't see as possibilities at this junction for various reasons. Mika is obviously a no go, as are Sarah's sisters. Chloe isn't a hard no to my knowledge, but extremely unlikely.