Artillery control item?

[k-bones]

Not everywhere, let's say 3-4k. Leave the numbers of mana etc for later, my point is to make that building a real must in some strategies and an important target for defending team. Factories are often unreachable, so that one would be as important as they are and easier to kill. It is usable for the whole team and eases base destruction (letting you pick some good tanks not so good at basekill), while still being counterable.