Sorry, but elite vehicle crew upgrade by far holds the title of most useless ability in the game. by far!
that entire doctrine is useless., assault engineers have no value besides demo charges. but once you reveal your assault engineer its obvious that you'll be building those because why else would you bring an assault engineer?
the tanks you get with it are not really that good, especially consdering you can get the jackson or sherman for cheaper/faster. The sherman bulldozer abilities feel interesting, if it could also knock down buildings and hedgrows it could be a really cool unit- but they left that out. instead youre supposed to like decrew it and buy SMGs or something.