Hello Colin,
thanks - ok, that does what i was looking for!
Of course you normally wouldn't want to do so in general.
But i want to create a completely "open" SSID, for an isolated VLAN that's only tunneled through the network to a dedicated gateway with no other connections possible whatsoever (also inter-user-traffic in that net is being denied).
I only care about bandwidth / usage, any further security issues (access-control, firewalling etc.) have to be dealt with behind that gateway (and they are)!