Why not look at CDC's reason for the condition? In the decision notice, they said:
4 Prior to the occupation/use of the proposed car park, a scheme of on street parking restrictions shall be implemented broadly in accordance with the details contained in Appendix J of the Transport Statement/Assessment.
Reason: To ensure that safe and suitable access through Kemble is maintained as a result of the scheme hereby permitted in accordance with paragraphs 32 and 35 of the National Planning Policy Framework.
Well, that provides a reason not to bother looking - it makes no sense, because the new car park has better access; direct from the A429 rather than (as now) through the village or from the north.
I practice, planners tend to exploit their one chance to affect development - the planning decision - to bolt on a few goodies out of their box (marked "planning guidelines" or "policies"). They also (as in this case) cite these as reasons, whether they fit or not, because the real reason may not have one. Then they approve the whole package, with no account of which bits logically depend on which others.
But in this case I can think of two aspects of the new parking that do logically depend on parking control, because what is approved might make things in the village worse. "Worse" here means worse than some other possible proposal, not the status quo ante.
One is the size - if even more parking will be needed within a short time, the planners will ask themselves whether they should have insisted on that now. The other is the charging - if a hypothetical expanded car park might have been free, or cheaper, then the one proposed (I assume at much the same rates as now) might only be approved if it does in reality stop on-street commuter parking.
The consultants' study shows you how this works. Appendix J, on the parking control scheme, (though weirdly entitled Parking Schematic) includes:
A parking scheme in the Kemble area of Gloucestershire is needed in support of proposed additional car parking at the Railway Station. A review will be necessary and should include a number of consultations with local residents, businesses and other organisations in the neighbourhood.
The main existing issues with parking arrangements in the area arise from rail users fly parking on quiet, narrow, nearby residential areas, to avoid paying for parking at the station. If the car park arrangement were to include charges, the problems with fly parking could well make the current situation worse or intolerable, preventing safe assess for emergency vehicles.
To address this issue, particularly rail users parking on the street, the County Council has requested a proposal for a new parking scheme covering an isolated area of Kemble. These proposals are presented for inclusion in the Transport Assessment. Neither a pay and display scheme, nor a permit scheme are desired.
Note the bit that says "if the car park arrangement were to include charges, the problems with fly parking could well make the current situation worse or intolerable". What the planners were thinking (assuming AKS Ward Construction Consultants have understood it correctly) was that charging for the new parking could be used to trigger the parking scheme, even if it is needed even more for the old car park (which provides them with no leverage).