Ok fair enough. With me, I put my reg in my mouth to swim out to dive sites as I always have heaps of air (can't remember the last time I ended a dive based on my remaining gas). This might be needed in other places but for the diving I do, if I want to see the bottom whilst swimming out, reg is fine, just don't need the extra air
With the heavy chop, I have had long waits on the surface and if it is choppy I keep my reg in my mouth or I time my breath with the waves. For the former, I have never been in a situation where I couldn't sit on the surface breathing off my reg for a long while. So I guess if a helicopter flies past me, I will just keep my reg in my mouth also.
On the other points, to clarify, for the mouth to mouth, are you talking about in water transportation for the first point on this?