I have a wifi router (TP-LINK WR740n) which is able to control bandwidth to avoid problems between gamers and torrent and streaming video users. All users connections are wireless. Also, there is no "internal" traffic - between users. Unfortunately, its WAN port is not working anymore due to a lightning rain. On the other hand, it could still work as just an access point and could provide internet connection through one of its LAN ports.
Will it still be able to control bandwidth? Or, does the traffic need to go through WAN to be controlled?
Another possibility would be to use WDS mode instead of a LAN port, but I suppose the wireless router is probably even less prone to control the bandwidth of the clients (that will appear as clients of the master WDS).