I think the reason you can't get two maneuvers for one action is that meneuvers are an integral part of the Fate point economy of the game. That is, you are basically getting a free Fate point worth of benefit by performing the maneuver, but that's OK because you're trading in a whole exchange worth of activity to get it. This is roughly the equivalent of accepting a self-compel to fail an action. If you were able to place multiple maneuvers in an action, then it would be too powerful comparatively.
Or at least that's my interpretation.
By the way, you might want to take a look at the Overflow rules (YS214), which allow you to get a bit more out of a overly successful roll, which could apply to high maneuver rolls. At first I thought this might be your answer, but I see that the Overflow rules specify that the bonus 'action' must be the equivalent of a supplemental action, so using it to place another aspect is out.