Which voicemail app are you running? I have a Pure Edition Moto X 2014 on AT&T, and I use the app, "AT&T Visual Voicemail" and it has never given me any trouble. The voice to text AI could use some work, and the app is horribly ugly, but the app does not crash.
Regarding messaging apps, there are dozens to choose from.
I don't know the details of your particular situation, but I think installing the AT&T ROM on a Pure Edition phone is an awfully drastic move to get two "very average at best" AT&T apps to run on your phone. I think you would probably be better served with an alternate solution, i.e., figure out why the VM app is crashing and fix that issue, and find other apps that are almost assuredly better than anything AT&T has cooked up.