Opinion of assault engies? I've not used this commander at all, curious as to why you went both lieutenant and cap, could have just gone captain and supplemented the lieutenant with a fifth rifles or assault engineer squad?
I think they're too expensive for what you get. Same goes for demo charges. I got the lieutenant for his firepower and in case I needed machine guns vs the gren spam. Five rifles would probably be fine too, but in this game I had tons of fuel to spare so getting both officers was no big deal.