Great questions, and either I'm not a good enough CPA to understand or this is a scenario that there is no good guidance on.
Possibly if we look back at what happened when the IRS first codified how currency trading works, we could get an inkling as to how it would work.
All I can tell you, is that the IRS will certainly make sure we give our pound of flesh no matter how it works out!
If you or other CPA cracks that code, they would get a lot of business!