Where do you set the default vault for new items?

I was a bit frustrated yesterday to hit this problem, so today I'd like to elaborate a little more on how I ran into this, because I think it could lead to some possible different solutions other than to be able to specify a default vault for new items.

What I was really trying to do when I ran into this issue is have a single shared vault, shared with my wife. I've been using 1Password for quite a while, and had a personal vault (only) and personal subscription. But I wanted my wife to have equal access to that vault, including from her Windows user profile on the desktop computer that we share at home, and that didn't seem possible because 1Password installs under my own user profile, without an apparent option to install it under All Users. We definitely don't have a use case for private, unshared passwords -- a key motivation for us using a password manager is for the other person to not be in trouble if something happens to one of us. After some research, it seemed that the only way for her to have access would be for me to upgrade to a family or team plan, so I did that. When I did that, I expected that I would then just be able to grant her full access to the existing vault I've had for years. But I found that that's not the way it works. Upgrading to the family plan ended up with each of us having our own private vault, and there was no way to delete or share those. So I had to move all of the items from my personal vault to a new shared vault, then give her full access to that vault as well. Leaving us with one vault that we actually want and two vaults that will always be empty unless one of us makes the inevitable mistake of accidentally creating a new item in our private vault -- which led to me chiming in on this thread.

So that brings us to alternate ways of solving this. The first and most straightforward from my perspective would have been to just be able to install 1Password in the All Users windows profile on our shared desktop so that we could both use the single pre-existing vault I had there. I understand that that may not work for you from a licensing/sales model perspective. If not, there are still things you could do that would allow me to have what I really want without needing the default-vault-for-new-items feature. If vaults in a family or team were just vaults, without a built-in and unchangeable notion of being either personal or shared, and all vaults could be shared or deleted without restrictions by authorized administrators, I would have what is my ideal solution: a family account where there's only one vault, that I could then share with my wife, and no other vaults such as the unwanted "Personal" ones we each have now. I'm not sure why it seems to be a good idea to force people to have a personal vault they may not want, or to make an arbitrary built-in distinction between shared and personal vault, instead of just having one kind of vault that people can either share or not as they wish. I also don't understand why there needs to be a kind of vault that can't be deleted. I can understand how it would be good to have a feature where you can't delete your only remaining vault, to avoid accidental great sadness. But I don't understand why, if my wife and I want to have just one vault, and to share it, we are prevented from making that choice.