I think most people don't have a clue what 718 is anyway!
I'm pretty sure I don't have a clue myself what 718 means. Something to do with the marketing people reacting to the engineers' decision to go with two less cylinders but turbocharged. After all, they never apologized for going from oil-cooled to water cooled on the flagship 911, let alone by dusting off an old model number.
I think "718" must be some sort of code for "really, it sounds almost as good..."
I have the model delete. either people know it's Boxster or they don't care.
That said, I think since it is more than a base model I'd get the OE badging and have it removed an re-centered with just "GTS." Probably a good nod to considering resale value on a car you've sworn you'll never sell.
EDIT: given the cautions about re-using the letters and the possibility of the original lettering leaving a shadow, I think I would order the car with the model delete and buy a new letter set for a PPF installer to apply just the "GTS"