If all equipment and chassis are also available for cbills it should be fine. They can consider compensating for different loadouts by giving a cbill kick-back for the difference to prior purchasers if the cost goes up on the new one, and to future purchases if the new build's cbill cost is lower. Pretty simple twice a year calculation to do, and probably wouldn't even be necessary as its a bit unreasonable to expect that kind of thing, you get what you pay for etc.
Edited in the new treb champion into OP.