You are right financially, it would be a boom for owners (and if they do it right, for players as well).
It's honestly, probably a good strategy for the general fan/public.
You are also 100% right that if they can find a way in the CBA to influence more competitive teams, then a larger playoff tournament might actually be OK/work, but I highly doubt that we see teams becoming THAT competitive over this CBA.
Drama will still happen, and in your scenario it will probably happen more often.
But for me, as a diehard loving baseball fan, I live for every single MLB game in the season. I love the season meaning something. The idea of half the league making the playoffs and taking away games from the season kills that for me. I would hate this down to every bone in my body as baseball is the only sport I follow/love. It would honestly make me consider not following baseball long term. So I am very anti extended playoffs even in light of a sound argument for it as I think it will water down the regular season, which, for me, is truly why I am a baseball fan - for the deep, enduring regular season.