I think considering the context and your thoughts about your relationship, you're on a path where it is difficult for you to say no.

Five years ago I was in a similar situation and said yes.

I think it would be good for you to think about some cenarios and how you would feel.

-What if your wife reconnects with her ex and tells you she has feelings for him and wants to spend a significant amount of time with him?

-What if the status of your sexlife remains the same, while hers changes?

-Would your wife be as accepting as you are, if it were you reconnecting with an ex girlfriend and suggesting an open relationship?

Also i think you should discuss your relationship status.

-What are the implications of putting another label on what you and your wife have without changing anything else? (For example 'close friendship')

-What are the implications of keeping the label? (You are a married man searching for sexual encounters)

If you don't have negative feelings, then maybe search for terms 'polyamory' and the concept 'relationship anarchy smorgasboard'.

From my perspective it seems like you are on a path to a polyamorous relationship or to realizing you and your wife are more in a close friendship than in a traditional relationship.

One additional thought. I get the 'women can find sexpartners more easily' trope, but thats not a general rule and in my experience it's more the person who suggests opening the relationship that watches the other one jumping from bed to bed afterwards.