A better solution is to leave the vest buttons as they are, and tailor the back panel of the vest to snug up the fit an inch or two. If too much fabric would need to come out, additional fitting can be done along the side seams, under the arm pits.
Trying to turn the vest into a double breasted, or simply moving the buttons over, would, as you note, raise the height of the vest at the throat. Additionally, the "points" at the bottom front of the vest would look wonky, even if they overlapped perfectly into a single "point", when the front panels are overlapped in such a double-breasted configuration.
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