If you roam for the video streaming then it should ok.
If you plan for the internet roaming, then you should make the 40APs just purely work as AP, you have to centralize ip addresses and authentication by different server.
But, if you plan for the video conference or the tel-conference. you should forgot about this.
I have to use PDAs in a warehouse. The PDAs use VNC-Sessions to connect to a Server.
It is important, that we do not losse connectivity, when we change the radio cell.
At the moment, I have loose packets, when the client starts roaming. If I use WDS, there is no problem, but I think WDS with about 10 APs is not a good idea…