They have not decided whether the answer is yes, multiboxing is fine, or no multiboxing is not good.

Which essentially tells boxers to skip the game initially, if you require boxing to play a game. There is no point in purchasing five copies, unless they are fully refundable... which probably won't be the case.

I would think the best strategy would be to allow boxing.
But set the game up, so there is enough going on that those who want to box get a large advantage over a single player, which makes it worthwhile to box.
But that five different players will usually be stronger, so boxers don't automatically dominate all facets of the game.