Thanks for getting this started Jay. Here are some answers:
I can't think of a scenario except perhaps a situation where your boat was fouled somehow and pushed you OCS (to avoid collision or something).
Nope. Check RRS 62.1. The only way you can get redress for anything caused by another boat is if there is injury or damage, or if they are penalized under RRS 2 (sportsmanship) or a penalty or warning under RRS 69 (gross misconduct). Weird as it sounds, if you get rammed from behind and pushed over the line, you get no redress unless there's damage, injury, or if you can prove it was intentional (good luck with that, BTW). Incidentally, this is the same for any flavor of OCS.
Perhaps avoiding a potential port-tack starter near the pin and you headed up to avoid contact, and went OCS
Nope, see above.
Would having your protest flag flying at the time of the OCS help the later decision?
No flag needed for requesting redress per RRS 62.2.
Mike