All that may or may not be so, but I doupbt any president would do anything more than simply dismiss any military officers that refuses to follow his unlawfull orders untill he finds one that will.
You have to remember Linclin fired a lot of generals until he found one willing to invade the south. It would probably be easier for a modern “president” with linclon’s example, and far fewer virtuous military officers.
The other thing they changed was they started moving all the military officers around a lot and frequently so they did not form any attachment to any community they might be ordered to suppress and/or attack.
The Federal military post-Lincoln has really been transformed into an insidious institution designed to uphold and defend Federal control over the people & their States.
This is why we conservatives are going to have to start seriously looking at letting the Federal military collapse, transferring most of their assets to the state National guards, and then reasserting State Control over officer selection in the National guards.