Yeah, I would be legitimately happy for a bisexual harem ending with Alice, Amelie, Clara, Crocell, and Eiko. The thing is Iruma's way too pure for it. Chadruma might be able to pull off a harem, but I'm unsure about our normal sweet boy. I think that Alice would be fine with it, Clara would pout and be jealous but secretly still be super happy, Amelie might be genuinely opposed, Eiko would be a little sad but happy to be recognized, and Crocell would flip around.
In the end, I think a harem ending is possible but unfortunately, very unlikely. I don't think Ix would be part of it either way, at least in the raws, since she doesn't seem to be gunning for Iruma like half the rest of the cast.
One thing I really want to see is Opera going really mama cat for him. She tries to hide it a little bit but I'm very sure she loves him just as much as his grandpa.