If the rifle is in its original configuration right now, no matter how worn, it will still have some collector value. If you modify it in any way, that value is gone. If it has already been modified, then the damage has already been done, most collectors would not be interested. I personally would not add a pad, 30-06's don't kick that hard IMO. If you have an issue with the recoil, then wad up a towel and jam it under your shirt, works like a charm on my .375 H&H. Also, everytime I tell myself "I will never sell this gun," I usually end up selling it.
Jared