I already explained that if someone makes an automated engineering tool, all users of that tool are at least as powerful as some (U)FAI based upon this engineering tool.

Think of the tool and its human user as a single system. As long as the system is limited by the human's intelligence then it will not be as powerful as a system consisting of the same tool driven by a superhuman intelligence. And if the system isn't limited by the human's intelligence then the tool is making decisions, it is an AI, and we're facing the problem of making it follow the operator's will. (And didn't you mean to say "as powerful as any (U)FAI"?)

In general, it doesn't make much sense to draw a sharp distinction between tools and wills that use them. How do you draw the line in the case of a self-modifying AI?

Addition of independent will onto tank doesn't make it suddenly win the war against much larger force of tanks with no independent will.

Reasoning by cooked anecdote? Why speak of tanks and not, for example, automated biochemistry labs? I can imagine such existing in the future. And one of those could win the war against all the other biochemistry labs in the world and the rest of the biosphere too, if it were driven by a superior intelligence.