I think your math reaffirms what I have been saying which is essentially agreement with Kinsella that the numbers are not realistic. The Liberals would have to wipe out the NDP, most suburban conservatives and win 40% of Quebec.
Sure it is mathematically possible just as any number but this is simply not realistic. The point remains that a Liberal majority has to be constructed in Quebec and the BQ as long as they exist take that off the table.
In terms of what is realistic-- rather than a perfect storm which is dependent on other's misfortunes is essentially what is in the hands of a "great" Liberal leader. No matter how great the Liberal leader is and the message without a catastrophe in the other parties you cannot bring in both the Conservative voters you want while wiping out the NDP-- there are no policies that can do that since the voters fundamentally disagree. How do you deliver what one group wants without alienating the other?
A brilliant Liberal leader and campaign could achieve what I suggested at the start but that is short of a majority. To eliminate the NDP and the Conservatives from Quebec while bringing the BQ down to 40 seats is a tall order but you are asking or more than that -- you are saying the Liberals would also have to eliminate the NDP and most Cons from Atlantic Canada and the West-- including bumping off the Cons in significant areas of Manitoba and Saskatchewan and even Alberta without letting in the NDP just to get a bare majority. It is hard to imagine the Cons that weak without the NDP coming up. Some of it is a matter of the lack of fear and progress of other parties-- akin to putting the genie back in the bottle.
In any case I think this exercise illustrates that what the Liberals have to do to get a majority is so far beyond what a reasonable expectation of success would be that they can no longer reasonably expect a good campaign to end in a majority. Remember that this was the bar-- you had failed if you did not deliver a majority. Here we are far from establishing if a good election can take them that far-- we are discussing if even in the best case scenario if it is even possible-- the bar has changed.
So to has it changed for the Cons. While a majority may still be possible or more easy for the Cons, it is much harder than it was in the days of Mulroney who cobbled it together without the BQ. It is arguable that Harper's last two campaigns were indeed enormously successful and it is the electoral landscape keeping him from a majority not his own weakness. Yes, if he had beaten back the BQ (no arts cuts for Quebec) he might have done it -- barely. But the task even for the Cons is much more difficult than it used to be.
All that said, hopefully eventually the parties will learn to produce stable coalitions rather than unstable government or hostage government as the Cons have put together over the last while where they do not have the support of the House but they cow the House in to not expressing that lack of support formally in order to avoid an election. This is an important point that needs to be made in that the current government has managed through intimidation to govern without the support of the House for so long. That is not a normal minority, it is a dysfunctional one. It did not come from compromise but instead threats, tactics and perhaps cowardice and incompetence in the opposition. That is much different than a working arrangement or coalition in the House.