Can I permanently disable the cell/radio of my phone?
Looks like someone already figured this out and made a script using Script Manager that runs the script on boot. It turns the radio (cell) off, just the same as activating airplane mode, except that it leaves all other wireless settings alone (that is, bluetooth, wifi, etc).

Or you can install a flashable zip described in this forum that you load in recovery mode.


  
  Removes unnecessary apps (Messaging.apk, Phone.apk, TelephonyProvider.apk, Mms.apk, TelocationProvider.apk)
  Completely turns off cell radio on bootup
  Installs the radiooptions binary in case your ROM does not include it
  Prevents emergency calls and 911 calls (good for giving your kids your old phone to play with)