To compensate for a non-flat spectral response of a radiation detector you can not do some post-measurement correction calculation unless you know the spectrum of the radiation source. The only way is to use a dedicated optical filter before the detector that fixes the non-flatness of the detector response. Such filter-detector combinations are usually very expensive.
I still think that you under-estimate the importance and difficulty of integration of the radiation in total light output measurements.
Anyway, I hope that someone will do all those nice things that you propose (not meant in a cynical way ), thanks for the suggestions and discussion, I hope it will be picked up by someone.
Me, I have so many nice little hobby projects on my list that for UV tests I will stick to what I do now until someone else does it better (hence the mention “final” in this threads title).