I can't think of any awesome advice at the moment, but I did start dating somebody who's partner I did not meet early on, and I will never do that again. I expect to meet my partners spouses (and hopefully other long term partners) before it gets physical, I expect to meet my husband's dates before they get physical (and vice versa) If I was not married I would probably not have this criteria for my partner's partners, but I would hope for it.
Really if this is what you prefer then that is good to know what you like. It makes a lot of sense to a lot of people, so your husband might want to learn to get comfortable with it, and sure he might come across awkward now and jinx a potential relationship or two as he learns to be comfortable discuss the need to meet his wife for coffee, dinner, or whatever... but that doesn't really compare to the fact that you will have peace of mind and he'll know his live in partner will feel safe and happy and everybody involved will know that it's OK to pursue romance. I am more interested in a family/friend/group feeling among metamours, as there are only so many hours in the day, which means I feel the need to at least know these other people involved with the ones I love on a "hey how's it going?" basis.
Happiness will never come to those who fail to appreciate what they already have.