Another solution that might be more palatable than allowing someone who just lost their own district to become PM is to normalize having PMs from either of the Houses of Parliament. Iām not sure how Canada elects its senators, but if you make that as province-wide PR then party leaders can be decently assured to get a Senate seat. (Actually, I checked and Senators are appointed by the Governor-General on the advice of the Prime Minister; constitutional convention might make for the leaders of any parties represented in the Commons to be guaranteed a Senate seat).
Another solution that might be more palatable than allowing someone who just lost their own district to become PM is to normalize having PMs from either of the Houses of Parliament. Iām not sure how Canada elects its senators, but if you make that as province-wide PR then party leaders can be decently assured to get a Senate seat. (Actually, I checked and Senators are appointed by the Governor-General on the advice of the Prime Minister; constitutional convention might make for the leaders of any parties represented in the Commons to be guaranteed a Senate seat).