I've never run into any limitations using my N4 as a wifi-only device. You still have access to Google services and any app you'd like to install from Google Play Store. You can remove the phone and messaging 'icons' from the home-screen, but the the features will still be installed on the phone and accessed from settings. There might be a way to uninstall the stock messaging app, but just looking at my phone for a few moments I couldn't see how to do it.