You could extend the neck out another fret or 2 if you wanted. Visually it looks fine like it is but IMO most players prefer a little more access if possible. You have to weigh whether that is important to you from a marketing standpoint.
There's not a lot of meat supporting this neck and structurally it's not a problem even with 8 strings. Starts out at 1/4" thick (less under the screw ferrules) at the 15th fret and tapers to 3/4"thick at the 18th where it meets the cutaway. Body is poplar. I wanted to see how thin I could get away with, neck screws are 3 different lengths. My NR is similar.
How about if the P/G is similar to a 59-60 EBO, touching the neck and cut around the pup?
edit:actually I may be doing something similar on the SS 8er I'm building.