When I was young my family occasionally ordered this breed. I didn't understand much about them then, but now I grasp that the way they're produced really stacks the decks against them for long term health.
Having said that, and please bear in mind I haven't done this, but I have a few thoughts ... maybe you could check these out with a vet to see if I'm thinking along the right lines ...
(1) Get a good b-vitamin supplement / notably biotin for this bird. I understand that these rapid growth birds can benefit from this greatly, as it helps cut down on the possibility of them getting bad legs.
EDIT: Also - consider adding a good general vitamin / mineral supplement - since this rapidly growing breed will need everything it can to keep it's body healthy.
(2) Rather than limit the chicken to tiny bits of food very infrequently - which would seem hard for a chicken to cope with - consider that if the bird wants to eat constantly maybe you need to supply it with a constant supply of lower protein food. For example, maybe foraging through the lawn every day would be a way to keep the chicken happily eating,without providing the high-growth concentrated food all day long. (Of course a balanced ration should also be given in addition to foraging)
(3) One of my chicken books tells the story of a lovely sweet hen raised as a pet which ultimately expired from heart failure. I think you might want to find out WHAT might decrease the chances of the heart failing. I mean, even people who are genetically disposed to heart problems can take steps with food and exercise to limit the possiblity of failure - so why not the same with a chicken?
They can be incredibly sweet animals. I'm sure one of the ones I be-friended as a child was a cross like your friends. Very loyal and gentle - came running when I'd call.
Hope this might help you think about ideas for your friend!