For the most part the epmp AP is just a bridge. Your tower side router would be the relay point.
Option82 on the AP allows for per AP dhcp assignments by inserting the required information into the request.
Those are part of the wifi specifications for 802.11.
There is no example for this, the AP does not make changes to the packets and has no settings to do so. The SMs have three modes, bridge/nat/router. Bridge does exactly that, NAT makes the SM act like a home gateway and router makes it act like a simple router but does not partake in routing protocols.