Assalamu Alaikum
Yes I would. I used to be a little open about it before anyways, but I feel moreso now.
The reasons are because I love Allah more than myself, and I love my husband more than I love myself. I also know that it's something that I can handle inshallah. Jealousy is not something my husband has ever made me feel, nor my family, and it's not an easy emotion for me to feel because I'm thankful for everything I have. Emotions change overtime, I don't want a little emotion to be in the way of something that could be good for me or lead me into jannah inshallah. I know that if it ever came down to him wanting a 2nd wife it wouldn't be for a frivolous reason, and I know his character is the type that honestly would be a person who would be capable of doing it the right way mashallah. The only thing I want from my husband is for him to remain as he is or become better than the way he currently is in piety, kindness, respectfulness, etc.
I also think sometimes if a woman can accept being a 2nd wife, then maybe she is in more need of having a husband than my husband is of having a 2nd wife. There are things we humans can only see on the surface of a situation, but Allah let's things happen the way they do because he knows the entirety of the situation and the pureness of the people involved, and how could I ever argue against what I can't see??
Before marriage, I'd play with the idea of actually having someone there who'd be like my sister, and we'd help each other in our iman, and raise our kids together, etc. I think positively of it all because it's a part of Islam that is halal, and I'd prefer this over my husband doing something haram. Plus, my husband did marry me, so if he married anyone other than me, I'm sure she'd be just as awesome
Scenario: If I had a husband who let's say just wanted a wife for his own personal reasons, I'd still be open to it simply because I'd assume there's something that I could not fulfill that he was able to find in someone else, which I'd be ok with because I'm not perfect. As long as my husband is pious and pleasing Allah, that is more than I could ever ask for because I'd know he'd fear Allah to wrong either one of us.
Scenario: If I had a husband who was not all that pious (kind of difficult to think of), I would not mind him to marry a 2nd wife with the sole possibility that she would help increase his piety. However, if this did not happen, then I would not want to be with my husband anymore.
Inshallah khair wa allahu a'lem.
fi aman Allah
w'salaam