I cant see any difference between a man or woman having more than one wife? Both are OK with me, as long as I am not involved :).

So, what are the real concerns about having more than one legal marriage at the same time? Let's say if all involved know about each other, are willing, and if no minors are involved?

I realize it is not the norm in society, it goes against some religious beliefs, and in some cases there are concerns for minors, as there should be for all minors in society. For discussion purposes, if one separates the cultish aspects out of the example, what are the concerns?