On the one hand collective responsibility demands a unison standing on the part of ministers, as government representatives.
On the other, the same ministers are answerable to their constituencies, as members of parliament.
The apparent reconciliation of the two is the fallacious assumption that the government will always act in the interest of all constituencies.
The supposed merit of having all ministers from the pool of MPs is the confidence of selection from a group that is already approved democratically by the electorate, in such a way that whatever happens after the ministerial appointment, the president will have the confidence of saying that I did not just pick any Tom, Dick or Harry, I selected among elected parliamentarians.The fallacy of this position is that too much stock is invested in electrocracy without actually vetting the validity of the other dynamics of democracy.Elected officials are not possesing unimpeachable integrity just because they are elected. One has to only revisit the fall of fromer PM Edward Lowassa from grace to appreciate how illusive the sanctification of elected officials can prove.Some would even go as far as saying elected officials do not posses unimpeachable integrity BECAUSE they are elected, their election being in a system that is full of corruption in which nobody can rise up the political ranks without shameful conducts, from nepotism to grand corruption.
The danger of a non-parliament based cabinet is real, in that all types of political payola schemes from simple quid pro quo to elaborate campaign finance misconduct will be at the mercy of the president.
The folly of the parliamentaly based cabinet is, it does not stop the very things it was supposed to stop, i.e it does not stop people of questionable integrity to get in the cabinet (How did Emmanuel Nchimbi and Nazir Karamagi get in the cabinet?). we have to chart a system to weigh the two in a comparative way to determine which is less injurious, which most benefial, by how much, and if a hybrid of the two with "best of both worlds" scenario is possible.
So in esence we now have the worst of both worlds.
On one hand the president is not free to choose people outside of parliament (Technically he has ten seats he can bestow on any Tom, Dick or Harry but in principle and fact they will become parliamentalians first before ever being able to become ministers, and even that laxity is limited, used sparingly and reserved for the likes of Kingunge, a few up and coming party stars and the odd disabled/ special interest person)
So on the one hand the president is limited to this pool of parliamentalians, mostly politicians and retired bureaucrats.He is missing out on a lot of talent from outside the parliament.
On the other hand the principle behind this scheme aimed at having a group of people that is already vetted and passed by the people.This vetting process and the whole idea is a big sham, it is as if the people are vetting on who is the most corrupt.
So that is how we end up with mostly bad apples, the Diallos of this world, the Nchimbis, Mkullos, The Mama Simbas and Hawa Ghasias, the Batildas and a host of other funny characters who would not pass an oral interview to be a CEO of a multinational's Tanzanian branch.
I say we remove this requirement, allow the president to pick anyone for the cabinet, but each selection be confirmed by the parliament.This way no one can say the people (or their representative at least) did not approve.
Of course the most important step to go even one step further would be to have a balanced, active and progressive parliament.