Why doesn't the player's union push for 12 batters in the lineup?

Player's union opposition is the practical reason given for why my idea about 8 batters wouldn't be proposed much less adopted:

8 batters and starting each inning with top of order fix two dumbest things on the field. Wednesday, December 2, 2020

Each of these two improvements will bring up the better batters much more often. Combined, they would improve MLB immensely.

8, not 9, batters fixes:

1. Pitchers batting.

2. Designated Hitter (DH), the "cure" for pitchers batting.

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To concentrate on the number of batters, I'm not addressing the other idea in the post quoted above:

Starting each inning with the top of the batting order:

Batters 1, 2, 3 bat at least 9 times a game, at least twice what they now do.

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Supposedly the reason player's union opposes the elimination of the designated hitter (DH) is because it provides a high paying job that otherwise would not exist. This model may have finally died with the retirement of David Ortiz in 2016 at age 40.

Then why doesn't the player's union advocate and negotiate the extension of the batting order from 9 to 12 without having the pitcher bat. Pitchers are getting paid for their pitching no matter how bad they are at batting. It's been that way for more than a century and is not likely to ever change.

Why have players, non-pitchers, sitting on the bench who will be used little, if at all? Put all or most of them in. Let 12 bat but only 8 play the field at any one time. Just maintain the batting order and they can rotate onto and off the field throughout the game. The bench warmers would get a chance to show what they can do and possibly earn more money. Instead of one high paying job, many better paying jobs.

What happens if one of them gets hurt? As long as the injury is not faked, either shorten the batting order OR put one of those good for nothing else pitchers into the game as a baseball player.

I am not advocating this. It would dilute the batting order and have the best hitters coming up even less frequently than now, which I recommend correcting:

8 batters and starting each inning with top of order fix two dumbest things on the field. Wednesday, December 2, 2020

Each of these two improvements will bring up the better batters much more often. Combined, they would improve MLB immensely.

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No, I am calling out the player's union for being tone deaf to the entertainment value of MLB. An 8 batter lineup would be far more entertaining than either having the pitcher bat or having a DH bat for the pitcher.