I think Hop building his as an exact copy of the movie car (except for things that would require chopping up the original Shelby) for himself is great, especially since he started with a real GT500. Selling them though, seems cheesy to me, and probably devalues Hop's car in all but his own mind, and those that know that it isn't just a bought one, and actually started as a GT500.
There are a fair number of people on this forum that hate El, more that have no real attraction to it, but think it looks nice anyways. These are the people who have different ideas, there are plenty of them.
I think the thing is that there are a couple of people actually manufacturing El, and it was a movie car, so touched a lot of people, some who didn't even realise mustangs existed (Like me, I was a 70s falcon man, XA-XC, mad max interceptors...), which is why you see so much of it. I'd love to manufacture my own style of 69 fastback variants, perhaps even only one variant, but noone will know about the car I want to build because it (most likely) won't be in a movie, and I probably won't manufacture it because I won't have the resources.
Anyway, point being, I think we see a lot of El because it is a well executed custom car (the one in the movie was original before it became so famous anyway) that appeared in a movie, and people are now building and selling them.
If I built and sold Els, I would also offer different stuff. Resto-moddy like El, slight body kits perhaps, big brakes, racing
suspension, polished wheels, different paint jobs, etc, different years too.