In my experience, disabling the radio does extend battery life, but some apps force close if the phone isn't in airplane mode, thus defeating the purpose. Maybe changing something else would fix this, but I don't know.
Removing the dialer won't free up ram, and it's removal can cause endless force closes. It's also required for Setup, so you can't add your Google account.
Sadly, the best thing you can do is put your phone in airplane mode. Maybe modify the phone to hide signal bars, but that's it. Also, not being able to make calls equals a risk of not being able to call 911. You may think that risk is small, but I have a healthy respect for Murphy's law.