There is nothing you can add to raise the VCI on this administration of the WPPSI-IV, as it is composed of the two subtests that were administered. That she did not trigger a discontinue (which I assume is the meaning of hit the ceiling that you are referencing), suggests that it is reasonable to conclude that information is a low estimate of her true ability, so that testing with a higher ceiling (such as on the WISC-V) may produce a higher VCI. The FRI was not calculated, as it requires both matrix reasoning and picture concepts, but I suspect that she would need at least an 18 on picture concepts to reach 145. In any case, since the VCI is below 145 (though I would not want you to think of this as "only" 140, since that is still extremely high!), it probably makes more sense for DYS purposes to wait a bit, until she is more likely to generate stable test scores, and until she is age-eligible to be assessed with a test with more headroom. Also, the FSIQ would be higher than the GAI only if she scored very well on the WMI and PSI subtests, and her lower block design score suggests that this would not be the case at the moment, at least for PSI, which is fine-motor-involved.
The stability or instability of her scores is more a function of her age and the developmental variability intrinsic thereof, than it is the number of subtests (though the FSIQ is the most psychometrically-stable score, it doesn't add enough to likely raise her score by 11 points).
The WISC-V, like the WPPSI-IV, is normed by age, so yes, it would distinguish between a child age 6-0 and one 6-11. If you choose to do so, when you re-test will depend partly on how much support you end up getting from her current placement (and thus how urgent the need for advocacy backup), and partly on her development and improvement in testability.
