As someone who works in the criminal justice system, the idea of not removing children without a criminal conviction horrifies me.
Plenty of crimes are committed without a conviction. DV - something which many children witness/suffer - has a very poor prosecution/conviction rate, because so many abused women withdraw their statements or decline to co-operate with the prosecution. I've seen plenty of women write statements saying they no longer want to have anything to do with the partner who has been arrested multiple times for serious assaults on them - often witnessed by their children - and then go back to that partner within hours.
I once sat with a very young woman and a social worker and support worker, as arrangements were put in place for her to go to a secure placement, away from the partner who'd broken more than one of her bones, and who was taking drugs around her toddler, and who she herself had been arrested for assaulting. It was made very clear to her that this placement was her last chance to avoid losing her child. She cried and made promises and was angry that people couldn't see how much she loved her child.
And then she popped outside for a cigarette, rang her partner who came and collected her from court and disappeared with him.
At that point in time, neither party had any convictions relating to the child or to violence against each other, because neither would co-operate - they just kept going back to each other, battering the hell out of one another, getting arrested, dropping the case and starting again.
DV convictions are increasing slowly, due to various changes in the process, and proactive policies in local police forces. But it is still spectacularly hard to convict someone, when the victim is flatly refusing to engage.