I'm wondering if there is a tweak or cydia app that will allow me to back up my text messages and later restore them when I set up at new, etc
including iMessages
Restoring from back up is always the wrong thing to do. I always start fresh.
I would agree that restoring as new is preferable over restoring from a backup, but to say that restoring from a backup is always the wrong thing to do is a tad overboard, in my opinion. It is a safety net, so to speak, and there are times when a person may need to restore something that he or she might have mistakenly deleted. It has its advantages and can be of good use is what I'm trying to state.