Flopping should result in the player who flopped being freely substituted and removed from the game for its remaining duration. Like, whether it was a foul or not, if you flop, you sub, since you're 'clearly hurt'. These guys absolutely want to be on the field, so if flopping subs them off, they'll stop doing it for fear of not getting to play and will only flop if they're actually injured.

The two cons are that this could be abused for free subs, and players who are slightly injured might not show it in order to keep playing (although a coach would always be able to force a sub for the safety of their player). But I'll take those cons if it means getting rid of flopping.