Cheating wouldn't be a massive problem. Just have the GM random up what card is drawn or the results of a flip/roll if needed. Plus, another big benefit of play-by-post duels is that you can do long duels in chunks rather than all at once if one person is short on time or multitasking.

Will work on my character, which will be a light-fairy deck with an archetype called "Celestial Seekers" which is based upon spies, space and magic because my mind is weird.