Kinda a few days late, since I don't check the forums much. But there is in fact a way to kick non-members. Sky, who has commented on the forums before has done it for his server which he coded completely by himself(rpg server). Just takes a bit of work. Chatted with him about this a few months back. Last I recall, he said something about having it done to specifically not kick the person who was newest and non-member, as to help build the community. It'd give a message to the player as to why they were kicked etc. Just a matter of him and jackie going over the details if this was something that's really desired. Though I was under the impression that it wasn't something cared for.
/end highjacking
As to keep on topic... Welcome, psuedo.
This sounds great. I've seen it done on other servers too. It will just auto-kick the person who's most recently joined that's not a member with a message saying that they are being kicked for a member reserve slot...and to visit the forums to become a member, etc.