The civilized ones, that is

Dear future hubster,

when we meet and decide that we are in this together, please know that I don't want you to retire from any of your friendships. I will love you for who you are, and that includes the friend you are to others. Why would I suddenly want you to be a different, or less of a friend?

This applies to your female friends as well. Even to your exes. When you choose our team, I want you to choose it because it's something you don't have, and want to have. Not to replace something that you have but think could do better, or something you lost but would like to have back.

Whatever I am to you should not change whatever you are to everybody else. If it does, then I'm afraid you have unsettled bills that you first need to take care of.