Your right about the 128bit encryption and wireless bridging not being available till the new firmware (which does come on new purchases now). As for password protecting SNMP management, you can do that and I think were able to on the earliest of versions.
Not too sure about MAC address restrictions, something i'll have to look into. I THINK I might have seen this in the config, but not something i'm too interested in anyway.
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Mk2a 30GB Blue. Serial 030102999