I don't think we should be discouraging people here.
Each case is different, if this father is not so good, then a parenting evaluation on both parents should be done, both parents should attend a parenting class.
I know my ex wasn't the greatest dad for many many years, drugs, drinking etc and went 2yrs without seeing our son. Now that we have moved he is realising how much he has missed in our son and is now trying to mend the relationship between both of them, he is now clean and has contact with our son.
I think this man may need a wake up call, and he will not get out of paying
child support, it just doesn't work that way.
Your friend needs to get an attorney, who is family law board certified, make sure not to just pick one, go see them in action prior to hiring an attorney.
Document everything, good and bad, people change during a divorce, some for the better others for th worse.
Each parent needs to do what they feel is right for the safety and well being of their chidlren.
Even if your friends ex and her get 50/50 who is to say he will actually take the kids??? If your friend is worried about when the kids are with dad, then have the local police to a wellfare child check while the kids are in dads care.
If this man has a drinking/drug problem or is emotionally or physically abusive towards his kids, then hopefully the courts will order him to get help, but even if he gets help, most of the time it will not work unless that person admits to having the problem.
For legal questions, you can post to Soc just make sure to use his posting guidelines.
**These are my opinions, they are not legal advice**