Apart from that, no idea. Since I know all the stock responses about child brides and other forms of abuse are going to be trotted out I'll just say up front that I hope we can all agree marrying an 8 year old to a 50 year old who beats and rapes her nightly is wrong even if you only do it once, so it's not really relevant to this discussion.

Perhaps an argument could be made against polyandry, at least historically, because until recently there was no way to know with certainty who fathered the child of a woman with multiple partners. Polygyny, obviously, has never faced this problem, and so it doesn't really surprise me that the latter is common and the former rather uncommon even in ancient times. In the 21st Century, however, a DNA test can quickly resolve the issue in either case, to the extent it matters (if finding out your ten year old son isn't your biological son changes how you feel about him, well, I hope his "other" father is better than you. ) And in the final analysis (we're not supposed to say "at the end of the day" any more, but I tire of just saying "ultimately" all the time) this is still America and I still believe my right to swing my arm ends where it intersects your nose--and not until. So if consenting adults want to have multiple spouses, that's their problem (though from a strictly literal perspective it's only legitimate for members of the Abrahamic religions to have multiple WIVES; multiple HUSBANDS is still adultery, probably for the reason I first stated. )

In my mind it's EXACTLY like the gay marriage debate: Why is the government interfering with peoples personal lives in America? Makes it a really fun grenade to toss in the middle of that debate, too; you'd be amazed how many people can make rational objective arguments for gay marriage and government non-involvement, then immediately recoil at the "ick factor" when it comes to polygamy. Heck, I have a good friend who's argued at length that just because Abraham had two wives (and two concubines, ) and Jacob had two (and a couple concubines, if you pay attention) and David had four, and Solomon had SEVEN HUNDRED, doesn't mean it's not adultery if a Christian marries two women. Apparently what's good for the Patriarchs is NOT good for the gander.

Further Edit: I'm really glad that the system for the family you mention works out so well, at least for now, but I expect that's the exception rather than the rule. The rule is probably more like Rachel and Leah, who didn't let a little thing like being full blood sisters stop them hating each others guts till the day they died, because they were constantly competing for Jacobs affection. If I had that waiting at home I'd probably go to Egypt, too. It's hard enough to find ONE person you get along with well enough, understand well enough, LOVE enough to spend your life with them. Every time you bring in one more you have to do that again AND ensure they can get along with each other. I don't think the chances any marriage worthy of the name can do that more than a few times are vanishingly small.

I don't think it's a good idea. That's neither here nor there to whether that (and a lot of other things I consider ill advised) should be illegal.