very plausible.

...would Wagner's fighters stick with him as he march on a Russian military base? Prigozhin's own mercenaries would be in the best position to know if they were bombed or not. If they knew that he was full of it, then this would be an ideal time to run off back to the Russian military. But, if it was true, then his fighters would probably feel that they were being set up to be a sacrificial lambs, because Russia would need to kill as many witnesses as possible.

Given the bad blood between Prigozhin and Shoigu, it makes perfect sense that supplying Wagner was not a priority for Shoigu. Of course, Prigozhin overreached by trying to call Shoigu on this, which escalated the dispute to the point that Prigozhin was calling for the ouster of Shoigu. The fact of the matter is that between Prigozhin and Shoigu, one of them was going to die.

but for now it's the "fog of war". Who knows whats going on. I think we'll get a better picture in a couple of days.

...the rest is going to be murky as this rivalry plays out in real time.

You might ask why Putin allowed this, but I think Putin encouraged this as a means of holding power. Notice that neither Prigozhin nor Shoigu are blaming Putin and both are claiming that they support him.

would be - would Russian forces (up and down the chain of command) willingly engage in such treachery against fellow fighters and countrymen - in full knowledge of 'political' (rather than strategic) motive?

Friendly fire is one thing ... A deliberate (and it is hard to imagine it otherwise) attack against compatriots ...

(another thought - given the wild hare that Prigozhin and Wagner have become - is there a decent chance that Wagner was in positions that they were told not to be .. ? And thus contributed in large part .. ? )

The person who is firing the missile or dropping the bomb would not even know they were hitting Wager forces. As far as the person firing is concerned, they could be hitting Ukranian targets. In contrast, the folks on the ground getting blown up would have a pretty good idea of what hit them and where the attacks or missiles were coming from.

It is possible that it was friendly fire given how poorly Wagner was coordinating with the Russian military, but as you note, if it was a sustained bombardment, then it gets a bit murky.

Finally, if you were either Prygozin or the Defense Minister, wouldn't you feel that you would need to kill the other in order to survive. Russian politics can be deadly:

https://www.businessinsider.com/list-of-people-putin-is-suspected-of-assassinating-2016-3

but that doesn't account for the blow back - and the shame of intra-force betrayal (with betrayal actually being far too mild - murder more like) - once the dirt and murderous intent is revealed. Again - you got people up and down the chain of command backing you on this murderous action? Or pretend like that doesn't matter?

It would be much, much easier (and make a heck of a lot more sense) to just eliminate Prygozin himself.
(which probably isn't actually too far into the future)

This points to Shoigu trying to dispose of Wagner. To get Wagner to stop march on Moscow, I bet Balurus is offering Wagner fighters a sanctuary so that they are not just thrown back in prison at end of war. The whole issue is who is the scapegoat for the war? Shoigu or Prygozin?

https://cnn.com/europe/live-news/russia-ukraine-war-news-06-24-23/index.html

based on what I am seeing on the ground.