"PR doesn't promote regionalism? Let me remind you that prominent PR models put forward for Canada -- including that by the Law Reform Commission, which you have elsewhere cited approvingly -- produce explicitly provincial lists for federal elections. That is not just amalgamated regional ridings -- some the size of countries -- which are bad enough. That is elevating regional jurisdictions at the national jurisdiction's expense.
Your One Big Confusion, Andrew, lies in thinking that meaningful choice can come of sharing executive power. When a company chooses a leader among, say, five-top candidates, it does not make the four also-rans vice-presidents with the power to veto the CEO's decisions. Especially if the also-rans have radically different ideas of the direction in which to take the company. It lets the leader implement his ideas and test their merit. If his ideas are wanting, the company turfs him out and chooses again, having learned from the experience. A company -- or any organization -- led by a collective that agrees on nothing would go nowhere and learn nothing."