Soapbox, becasue we don't live in an ideal world and very often it's impossible to be civil to one another.
I'm not saying it's not very very difficult to sort out, nigh on impossible for some, but then you have to weigh up what you think, or on evidence, what is deemed to be more traumatic to the child - seeing the parents either abject or at each others throats for a very long time, or having a temporary period of resettleing, while based in their own homes, until things die down.
I don't know. A child can't be split equally between two homes, that would be too stressful. I'm not saying it's not a tragic situation, but like marriage and partnership itself, people have to be prepered to compromise (often these days though, that's precicely why the relationship is failing).
And how many men do you honestly think would give up their careers to take 50% of domestic and childcare responsiblities? Realistically? There are some, but they are generally the exception that proves the rule.