For what it is worth as one of the prime movers setting up BCA, I am of the opinion that its remit was restrained by the preceding NCA constitution. The reason BCA was eventually set up was the termination of the insurance policy then run by BCRA and the consequential loss of access to caves where insurance was required. We used that crisis to force BCA into existence by obtaining a new insurance deal but instead of being focused on clubs, it had to be focused on individuals. (The legal set up meant we had to provide insurance as a membership benefit as we could not simply sell it.) So the consequential major change between the NCA and BCA constitutions was the introduction of individual membership. (Oh and the elimination of the power of veto on any business by regional caving councils.)
Keeping most of the NCA constitution kept the domination of the process of 'members tell clubs tell regional councils tell national council'. We were also forced to accept a two house set up where by individuals and clubs houses separately vote on topics at general meetings.
I agree the time has come to review that though I doubt if the current lock of a club vote will permit much change. (Unless their members tell them to do so.) And I am deeply pessimistic about breathing life into a new structure with the energy to do things. I accept we made Council far too large so discussion is never ending and decision making rare.