Can't be a huge difference in price, especially when you consider that major work like you describe is probably going to be priced high, coz the guy doing the work probably doesn't really want to do it...and there are often cues that makers have around their shop that they will let go at reasonable prices.
Besides, you cant have a collection of one.:grin-square:
Adding a veneer would not be an option. Adding ring work, as long as it is inlaid, is an option. However, most cuemakers would prefer not to go back and add inlays, ringwork, etc on a completed cue. Too many things could go wrong and then they would have to build you a new cue. The risk is not worth the $$$ they would get for adding additional work into the cue.
With today's technology, adding a veneer is possible. I am pretty sure Paul Drexler will do it. I know of a few others who could, but not sure if they would be willing. May be cheaper to buy another cue though.