Wouldn't a yo-yo universe violate the second law of thermodynamics? Basically, you'd have to figure that either the expanded or the contracted state would represent the state of max entropy, and there the whole deal would stay.
Why? If some force, like gravity, makes it collapse, it will do so. If something else makes it go Bang, it will do so. Why couldn't this continue eternally? Where would the energy loss due to some kind of friction go?