OK, so you're the one pushing for being poly with your husband... And the only "bait" you've got is the hot bi babe. Who would become the sister wife and he'd get to be coddled by both of you sexually and emotionally.
Now, you're ready to give up just at the idea that she might prefer you and he'd not get to have his poly fun.
Think about it. There are so many configurations of poly here, read around, read people's sigs for their relationship status. Some women have 2 bfs, some ppl are married and only see other lovers a few times a year. Some have FWBs and are dating others, trying to find another decent person. Some people are independent and not currently dating. Some are even asexual.
So, you've chosen ONE possible configuration and if it doesn't work out, your h will be so jealous, he'll bail. Well, jealousy can be lived with and then overcome and compersion can result. Takes work though. Many threads here on jealousy! Many articles in cyberland.
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
me: Mags, 59, living with:
miss pixi, 37