The minimum requirements canonically are that the sponsor has to be over the age of 16, not the parent of the candidate, fully initiated (baptized, confirmed, and received First Communion), not under any canonical penalty, and leading a life of faith (a practicing Catholic; if married, then married in the Church).
When I think of sponsors, I think in part of someone who can be a role model for what it means to live as a Catholic. And I think in part of someone who can help the new Catholic make connections in the parish.
You ask about having someone who is a complete stranger. While the sponsor may start out that way, I hope that as preparation continues for the catechumen or candidate, the sponsor starts to become a friend and a source of support.
I would recommend that each person being baptized or confirmed have his or her own sponsor at this significant time.
Your RCIA team should be able to assist you in finding someone. I’m surprised the subject hasn’t come up already.