Why would they allow your to move the regular sentry? The position of metal on a map was crucial to determine the best place to build and maintain a sentry. Now that has been made completley irrelevant. I can build up a lvl 3 sentry at spawn and put it wherever I want now. Valve has never drastically changed the original weapons in other class updates like they have here. They should've only had it for the new Mini-Sentry which is kinda useless anyway.
The engies are way too overpowered. If you go on a server, make sure they have an engie cap.