Your post was clear, it's the previous responders who have misread. As already noted, they sell 140mm stems and they are intended to be purchased and used. A lot of pros use 130-140mm stems.

A longer stem may create a slightly slower feel to the steering but you would be used to it within a ride or two.

Another misconception is the idea that changing the stem length affects the weight balance. It makes very little difference. The biggest contributor to weight balance is saddle fore/aft position, follwed by torso angle. The lower the torso, the more weight on the front.