im pretty sure thats not possible, 'normal buildings' give you 1 rankingpoints per culture/population used. You loose that population and culture as soon as you start the upgrade, not when its finished.
In the case of wonders you dont use (loose) knowledgepoints when you upgrade, thats why they originally didnt give you any rankingpoints in the first place. After popular request they decide to give them rankingpoints, by giving each wonder a certain amount of ranking points at each level. They matched that amount of points to the amount of needed KP, but that could have been something else they chose, could as well have been 100 points per level. so they cant give you points untill the building finished upgrading becuasee you still have the wonder of the previous level in your city till its finished.
I think the other way around (normal buildings only giving points after its finished) is more plausable solution, but i dont think they want to put that much effort for changing the ranking points for each building by fixed ranking points on each level instead of calculating it on the fly on cult/pop used.
Also im pretty sure this question/suggestion has been made in the past....