When it comes to a G1 pony who is common but in good condition, there is always some bit of personal morals that determines what you will do.
I haven't customized personally, but I have rehaired. I always wait for a pony with no hair to work with, rather than chop off the hair of one that is good.
So, I would wait for a baitier one to come along. Perhaps you could find someone who wouldn't mind trading up for a better condition one?