The ability to set guest sessions to be limited to some amount of time (4hrs, 6hrs, Xhrs).

This would prevent devices owned by local/neighborhood visitors to (accidentally or otherwise) continue to use my guest network beyond X hours.  It might even be made more simple to allow the guest network to purge all devices at hh:mm each day, and require a new invitation to reconnect.

Also, I second the other person's request of limiting the Guest network bandwidth to either an overall amount of bandwidth (no more than x% of total ISP throughout or max of XMbps per guest).