AP 420, only one visible SSID- hack available?

[tschaps]

I recommended a small school to buy some used AP 420s to put wireless in their school without breaking the budget. I knew that the 420 could do up to eight SSIDs and VLANs, but I did not know that it could only broadcast one primary SSID. :smileysad:

We had been planning to set up an open 'guest' network on a separate, low-priority VLAN. Some of the school devices do not connect reliably to the hidden secure SSID if we make the Guest network the visible one, so that is not an option. 

Doing some research, I understand that the limitation has to do with only one MAC address for the wireless side on the AP 420. Current model APs which do multiple, visible SSIDs have a unique MAC address for each one. 

We are stuck with what we have, and HP has not come out with the firmware update for the 420's in a while, so I am not holding my breath that they will come through with a solution. Just curious if anyone has heard of a workaround or hack? I just need one additional visible (broadcast) SSID. 

Thanks.