After playing the save I was having trouble with a while longer, I definitely agree, construction bots can be pretty strong in combat situation.

I still think smoother ability to protect your bots would be very helpful.. for instance, my railways are not safe, so i have to always remove personal ...

I'm annoyed that my construction bots run into battle to repair stuff and die, so here is my proposal:

Make construction bots ignore anything that's taken damage in the last x seconds.

It could be configureable/turnoffable or even require a technology, but I think it would be incredibly helpful ...