I think I remember reading somewhere that the hamster is the only rodent recognized as a domesticated pet, which gives it legal protection from cruelty like dogs and cats get. I believe that feeding frozen/Thawed or live hamsters could get you a fine and jail time just like if you fed f/t or live puppies and kittens.
I don't know where I read that and if someone wants to research it, could be interesting. Although I once had a snake that would only eat live pinks and my hamsters were breeding fools...
I figure if you can feed guinea pigs, you can feed rabbits. Seems like they are cheaper, I know that they are much more prolific.
I am told that for BPs, if you feed Gerbils, many of them won't accept anything else again. I've avoided giving my BP that option. At 17, he doesn't need anything disrupting his already hard-to-pleas-ness.