I like the proposal overall, though I have concerns about the effects of having lower ensemble values would have on scores and caption choices. I converted the final captions for my three corps for this season to the new values to see how the totals compared to your proposed values; World - 283, Open - 258, Class A - 232. I seems to me that lower ensemble values would not only encourage but necessitate more lower corps captions be used wherever possible *cough*not GE*cough*, which would ultimately just lower overall scores. Not necessarily a bad thing though.
I think keeping World relatively the same as far as ensemble values but putting more limits on Open and Class A in terms of lower ensemble values and artificial caption caps (as is for Class A GE currently) could lead to more diverse captions choices across all divisions. For example, limiting Open Class corps to only use captions valued of 35 and under, and 30 and under for Class A.