Ovinomancer
No flips for you!
According to Crawford, you can take the bonus action before or after the triggering action, though you must take the action and can't change your mind.
Heh. First thing that popped into my mind is reveal's macro. You know the one. /inside joke
Huh, well, I'd not have arrived at that particular unobvious conclusion myself, as then/if statements aren't something that occurs to me to consider. I rather liked the limitation on shield master that you couldn't manufacture your own advantage every round, but you could use it to control the line and assist your team. Especially given how easy it is to stack athletics for a fighter and how most critters don't have a good chance to stop it.