In general I agree, but the problem is with Hitler, Goering, and Himmler dead, the only Nazis with control over guns in a HIGHLY centralized state are dead; the opposition to the coup is headless, while the army, now severed of any loyalty to the Nazis, even if caught flat footed, isn't going to want to be led by any of the remaining Nazis.
The main problem, naturally, is the usual notion that one thing is the Nazi regime and another is the armed forces - as if there were no Nazis among the generals.
Even assuming that were true, and it wasn't, there would be plenty of generals who might think the best bet in this situation would be to play both sides, or to pose as a general who's faithful to our beloved late leader's ideals, in order to exploit the party machine against any other garishly uniformed competitors.
The other problem is the notion that only Himmler can command the Waffen-SS. There was a central command for the SS military units, led by a deputy of Himmler (Jüttner), and there were at least a dozen of men holding the rank of SS-Obergruppenführer, which is one step below the rank held by Himmler. In an emergency, Waffen-SS units would defer to this command and these men, all the more so if the emergency included the murder of Himmler. The rear-area SS und Polizei HQs and battalions could provide plenty of gun barrels, etc.