if you could manually do it everyone would just do it immediately all the time
so it's not like it'd be any more fun or anything
Its not like it'd take a couple rocket or C4, it'd take some time, and less of a "ooh cool building collapsing" and more of a strategic demolition. For example, since rockets would be fired quite a bit, the building's health would be slowly taken down, and eventually the building would collapse, this combined a group of enemies in side the building could cause a good amount of fun.
I'm aware that this isn't the best idea, but I was mostly responding to how GBH said that you could topple skyscrapers, when in fact, they topple themselves.