Is there a way to disable the hardware on/off switch for the Wireless interface?
No, you cannot. To sort of disable it you can phsically block or remove the hardware switch. There is no way to override the hardware disable button if rfkill shows hard blocked that is feasible for most people.
When you unblock it, if it gets stuck in some inconsistent state your best bet is to:sudo modprobe -r iwl3945 && sudo modprobe iwl3945
I have an hpdv7 and the wireless a)uses the same driver and b)hardware toggle works for me.