Being that most glues used by qualified cue makers are much stronger than the wood itself, I am saying it will not effect the playability at all if done correctly. Sure you could get carried away and go way down the shaft with huge pockets of inlays, which is not to bright, but most makers only use spliced v-groove points or inlays around the joint area. They do this for a
couple of reasons, one it looks great on some cues and styles, and two, it is the meaty part of the shaft area and would be no different than doing it to the joint area of the butt. Most of us stay in some what of a traditional style of building, so if you see this sort of thing most likely it would be a one off style show type cue or some one just having way to much fun and time on their hands!