I don't poo-poo evolutionary ideas automatically since I think quite a bit of adaptability was built into the prototypes of each family introduced into the biosphere. If bird wings evolved, I thought the 'started as stabilizers used while they lept after hopping insects' was the least absurd hypothesis. That does not explain the origin of feathers themselves though. They seem to spring up with the hook and barbule system already in place- except for fossils with down feathers which birds have today. How did the small biped dinos know they were going to need flight feathers?
That is a minor problem compared to proposing intermediates between the bird's continuous-throughput respiritory system and the in-out system of all other vertabrates.