It isn't possible to simply share the position, but I have heard of councils splitting the responsibilities. The limitation is that statutes say quite specifically that the chair must, if present, preside. The vice chair presides only if the chair is not present. (Other statutes say that a council cannot function unless it appoints a chair).
However, it has been known for councils to have a member who is not the chair nominated as the council's representative for civic responsibilities. So there is some scope for sharing.