Uhuru bosom buddy Muturi asked for Exec PORK to be leader of biggest party/coalition. Same as Wiper, Chap Chap (both want unfirable PM to run cabinet with PORK powerless but respected as English queen) while Nyong'os, etc want pure parliamentary. Same difference - unelected CEO. Only Mdvd wants flowergirl PM. ODM of course did about-turn to appease Gema - sleight of hand poor Pundit cannot decipher now. ODM will not oppose parliamentary Haji report. Governors and CoG care about more devolved %. Expect some Muturi variety of un-elected CEO disguised by directly elected figured.
Constitution was first amended bila makelele in 1964-69 - when Gema PORK and Luo had aligned interests - exactly same as now. That was a bigger wholesome overhaul than 92 multiparty, 97 IPPG and definitely 2010. It about alignment of the stars - as you argue against yourself here - all Kalonzos, Mdvds, Johos, Duales - back BBI for their own selfish reasons. With that coalition BBI will pass easy-peasy. There may be noises and decampings after that as 2022 take clearer shape.