Assured seats on party lists is a standard feature of proportional voting (of which I am an advocate), and one often held against it.

Finland has proportional voting but then seats are distributed on basis of personal preference voting (mark your prefered candidate, an the most prefered gets your lists first seat). Sweden has the same, but to a much lesser extent as  candidates has to pass a significant threshold to change position on the list, leaving power mostly in the hands of the party establishments.

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