It is clear that is an argument put forward by the mothers counsel. 
So anyone in a similar position ought to consider "putting forward any fixed firm plans about how he would care for the children if they returned." as a pre-emptive strategy and cover the objection of how it "difficult for him to do so" as for the mother's child support well obviously if she is no longer the primary carer it will affect her eligability but that is an irrelevant consideration really.