@ghnaf What these gentlemen are trying to say is probably that the attention, or focus if you will, required to give orders to said engineers is actually a core part of the skills needed to be good and that automating it would make the game easier, or less skill-based, or less interesting.
Of course, if they would actually bother to properly reply instead of trolling/flaming, you might have understood that, but that's just how it is when you touch some topics.
I for one would actually like such a feature, even if just to use it on non-competitive modes/singleplayer.
Just in case you weren't aware, you can almost already mix an engineer in your factory queue and move the attack order around as your army goes if you want to reclaim the battle zone—the fact that engineers won't be selected together with your army is helpful in this case (unless you hold shift).
If I remember correctly there was already quite an uproar a long (?) time ago when someone uploaded a mod that would you to select some zones for reclaim, try looking either in these forums or in the old ones if you are interested—the arguments used against it will be a good point of reference.