Instead, flopping penalties should be retroactive, assessed after the game is over in the form of a progressive fine structure that gets steeper with each offense.
There is no way in real time to discern whether someone genuinely got knocked over, whether the contact was real but embellished, or if it was just completely fabricated. A lot of times, legitimate, by-the-book fouls do not get called by refs unless the fouled player embellishes the contact to make it more obvious. The question then becomes, where is the line between embellishing a legitimate foul to draw attention to it and flopping?
The flop is such a subjective call that there's no way it should be made in game imo. As much as I hate flopping, you're giving the refs WAY too much power if they can arbitrate whether someone embellished contact, and if that rises to the level of a flop, since every ref seems to have a different threshold for what constitutes a flop and there is no way to objectively make that call. Refs cannot read minds, and you need to be very judicious when assessing penalties based on intent more than consequence.
They should review potential flops at the next timeout, just like they do for foot-on-the-line threes. It's the best of all worlds: you assess the penalty in game, you get to check on replay to get the call right, and you don't stop the game.