"First, I want to become much smarter. I want to be far better at solving any kind of puzzle or problem than anyone who has ever lived. Of course, I should not lose any of my other mental abilities (or physical abilities) when I gain this one."

To be perfectly hones being far smarter than anyone who has ever lived may not be that smart. I mean what's the competition? Francis Galton, Issac Newton perhaps Neumann? They didn't build superweapons on their own.

I suppose, and this will be a contraversial statment, the ability to manipulate people due to high inteligence should be our real concern. Analyzing and replicating the speaking abilties and charisma of Hitler or the transeferable skill and tactis of Napoleon/Julius Caesar/Alexander dosen't seem that hard and is a more realistic threat.