My two cents:
We should maintain the status quo exactly as it is, or we should have a 15-member Cosa where one member holds exactly one seat.
There is great value, I think, in having a system as we do where very small parties can still gain representation in our legislature. To make it otherwise is to exclude citizens who deserve to be involved with the lawmaking process. Principles 1, 2, and 3 could be enacted, I concede, under the status quo; I resist them only because I think that it is fair currently if more active MZs are awarded with larger shares of the seats.
On the other hand, if we reduce the Cosa seats to 15, then we should just commit fully to the idea: one member, one seat. To make that work, though, we would have to abandon the perfectly proportional seat allocation that we have now and replace it with electoral districts. Is Talossa ready for that? And wouldn't that conflict too much with provincial Senators? We could try the mixed-member proportional (MMP) system that the German Bundestag and, poignantly, the New Zealand House of Representatives use, but how much of these new constituencies would overlap fairly or unfairly with the provinces? Imagine a scenario where Talossa all but implodes on itself because the new constituencies gave some (un)fair advantage to a particular political party.
I am basically articulating that the status quo should remain, or we go all in for a unicameral Ziu with 15-20 seats using MMP. Everything else feels like a broken half-measure compromise that creates more problems than solves.