WW3 is gonna happen in a 4ft 125 gallon tank stocked with 8 larger tangs. There is no way around that. You can't keep more than one tang in a tank unless it is a 6ft 125 gallon tank, length being the more important of the two. With a 6ft 125, you can only keep a max of 2 tangs and they HAVE to be from a different genus. With a 180 you can do three tangs of different genus', a 240 4. To keep 8 tangs you need over a 10 foot tank and quite a bit of room front to back.
IMO to the OP, a mimic would be perfect. To me they are more colorful than a scopas, not sure why, but I don't like scopas tangs very much and I am not a fan of yellow tangs either. A lemonpeel mimic would look stunning in your tank as the showpiece of your tank.