said by docrice :

You want each client to be in its own /30? Maybe this is accomplished via dynamic VLANing and layer 3 switching?

This isn't exactly the same thing, but Cisco APs (at least the older 1230 series) have a feature called "Public Secure Packet Forwarding" also referred to as "client isolation" by other manufacturers. It's basically a way for associated stations from being able to communicate with one another. That should accomplish essentially the same thing as an isolated collision domain.