Adding a sugar solution will add fermentables and therefore will increase alcohol, but it will not alleviate thin body.
You might be better off to brew another batch where you mash much higher (and/or add malto-dextrin powder) to compensate, then blend the two batches together. Besides, if its a good enough technique for Jean-Pierre Van Roy to use, then I don't see how it can hurt to try it at the homebrew level.
my .02