Yessssss Marco is back! He already is used to being shot up with drugs to become a berserker so he may have an advantage against the referees here. As a wild card, if he takes enough handkerchiefs the people he takes them from are out and as long as they're still in, whoever Baku wants to preside (probably Yakou) will win.
That is to say, this game itself is a gamble: if a referee just hid until everyone else was down or fought the last person standing they would keep their handkerchief and win. But if they fight early they have to fight more people increasing their risk/reward. I think the author included the whole drug thing to explain why none of the referees are really taking the sensible, cautious approach.
It also reminds me of the Hunter exam from HxH... right after a Greed Island arc too...