Depends on who the someone else is and what the finished product looks like.
If the someone else cuts the groove right, and does a flawless job where you can't see the seam in the leather and everything is flush, I doubt the cue would loose any value.
I also doubt that it would change the way the cue plays. It's your cue, you can do anything you want to it to make it look, feel or hit better to suit your needs.
If you do decide on leather and dont like it, I guarantee you have no trouble at all selling here or on fleebay for more than your initial investment.
BTW...
You can put me on the "to buy" list for your wrapped or unwrapped Searing.