During 2010-12 implementation, MPs messed with Senate powers. Very short sighted. It was basically Orengo, Kiraitu, Nyong'o and ilk. Two short years later they were back as senators whining about powerlessness.
Obviously Senate should be the upper chamber doing all the vetting of judges, CS's, foreign treaties, etc - under presidential system. National Assembly handles money bills.
Under parliamentary, if we go full federal, Senate should be scrapped. PM and Exec are members of National Assembly so Senate become moribund like UK House of Lords - who double as supreme court to kill time. I think in UK it full of dukes, counts, earls and all such nobles or "lords".