I see where the op is coming from regarding the tax credits issue. The CSA currently count all household tax credits (including child and disability tax credits) as the income of the non resident parent along with any other earned income.
Therefore, a parent with care who uses the CSA gets not only the tax credits they are personally entitled to but also a portion of those paid to the household of the other parent. In some cases step-children of a non resident parent are actually paying part of the maintenance through their tax credits.
It does not matter who the tax credits are paid to or for, and this aspect of the legislation has been much criticised and challenged.
While it is arguable that working tax credits paid to a non resident parent could reasonably be classed as income. It does seem unfair that child tax credits including any disabled child tax credit supplements paid to their partner or spouse should be taken into consideration.
As far as I have read, the new rules will not include any tax credits paid to the household of a non resident parent. Only their earned gross income will be used in future to calculate maintenance.
The new scheme seems designed to encourage parents to reach private maintenance agreements between themselves and to reduce the administrative burden on the CSA wherever possible.
Should parents be unable to reach or keep to an agreement then they can use a collection service which will incur a charge for most (but not all) cases.
Whether it will work in practice however remains to be seen. I suspect that as usual with these things there will be some on both sides of the coin who end up better off and others in a worse position.