I raise my own feeders and have sold a handful as pets to people. I don't see any reason to ruthlessly separate "feeder" lines from "pet" lines. I'm going for the exact same thing in a rat, a healthy, well grown, good attitude rodent that grows well on decent food without getting ill.
My feeder rats all have to have good friendly attitudes. They have to grow well, have nice sized litters that grow quickly and stay healthy. Other than litter size, I don't see anything in that would not be essential to a pet rat, or even a show rat. Just because a rat is close to the ideal of "rat-dom" in size, shape and markings doesn't mean it's a lousy breeder or a slow-grower after all.
I do give my colony and feeders the best life possible. They all get premium food(Mazuri I order from a feed store), clean bins, fresh water, treats and 'stimulation' in the form of treats hidden in balled up paper or toilet paper rolls and such. I don't overcrowd them and I don't starve them or mistreat them.
The local "big breeder" of feeders also has pristine conditions and fat healthy calm rats. I used to buy my feeders from them and I was amazed at the quality of their "feeder rodents". I can say for certainty that they matched or surpassed ANY pet rat I've handled or bought. I have seen lesser quality "big breeders" in the past, but rarely seen any I would hesitate to buy from and none that I felt mistreated their rats.
I also have pet rats. It's possible to take wonderful care of your rodents to feed to your reptiles. It's possible to love a pet even if it's the same species that you use as feeders. It's like someone who has a potbelly pig but still enjoys bacon.