I can give you a specific example of my DH ex wife attempting what you are trying to do. I am not a lawyer but have a law degree - so dealt with my husbands case for him as litigant in person (the only part I was not permitted to be involved in were the actual court hearings. As these are confined to the concerned persons (the parents, social worker and legal rep of his ex wife (a direct access barrister)
His ex made the application.
My DH opposed it.
Reasons were provided.
Court hearing .
Ex wife put her case forward and her reasons why it would be in the childrens best interests .
New hearing date set.
Long statement from her lawyer setting out the utopian uplands of her planned new life following marriage to her fiancée who she had been seeing for 4 years but had never lived with her and the children. He worked overseas but was returning to be near his older children 200 miles from DH.
I wrote a 95 page rebuttal statement . Going through each point. These mostly comprised the financial gains she would have access to with the new marriage and how that would provide a much better quality of life to the children . Stuff like private schools, horse riding lessons. Ski holidays. Along with 'hands on support' with the children.
This man had spent a total of 10 weekends with them in 4 years. They were 12 10,9 7 at the time and saw us EOW without fail and had done for 4 years. They had sibling relationships with my three of similar age.
Second hearing . Judge read statements and asked if the father would be prepared to be the resident parent. We had already agreed between ourselves that this would of course be fine although not the best for the children. She was/is a good mother except for her hatred of my DH.. and the kids love both their parents.
Judge ordered social workers reports. Social worker came to us when the kids were with us. Also to his ex when kids were with her. Spoke to the kids alone as well.
Return to court and judge ruled that as the children had a 'strong and effective relationship with the father the application to remove was refused. He also added that if the mother required 'extra support' the father is the one who should provide it and would consider an application should DH be minded to make one.
He didn't at that time as felt she had lost a lot. Wish we had done in retrospect.
A year of massive unpleasantness from ex ensued. Then she married him and he moved in with her. He lived with her 6 months before taking up another post overseas . 'Couldn't live with someone else's teens'
They are still married but the kids tell us that he just isn't someone they want to live with . All late teen mostly twenties now. Mother flies out to visit her DH e every month and he does the same.
He never did stump up for the private schools.