For engineers (and only engineers), early testers requested that they wanted the engineers to have to be ordered to stop before giving new orders so as not to inadvertently reorder their queued builds.

Discuss.  

Not to bring up Sup Com again. But, the system they had is that Builder units would only be selected if you held shift with the click drag selection. Allowing you to select all combat units in an area without disrupting your builders. They would also be selected by a click drag if your box only contained builder units. I'm not saying you should copy that system but I believe it's a pretty good solution

That needs to be togglable since the vast majority of the times when a fight is happening, i want my engineers to continue building defensive structures regardless of being hit.

As towards the original question, i believe the best option is the military units take priority during selection, with engineers being ignored. Took me a full game to understand why my engineers were not responding to my new orders, and whilst pressing stop does not take much, its not particularly intuitive either.

Yes this is happend to me .

Almost every action i try to make with engeniers units or build  dont react to my commands.

I have to click several times to make just 1 action, and then the pan view left mouse click, also isnt help , bit confusing.