Is there a way to completely disable the dialer including emergency calls to make an old phone a "tablet"?
If you root the phone, go into Manage Apps and you can disable the dialer, it will remove it from the home page. Contacts can also be disabled. There are also numerous ways to put the phone in Airplane mode so it's persistent after restart.



Click image for larger version

NOTE: disabling dialer does not disable the emergency dialer, but airplane mode does.