repotting/Semi hydro

I'm considering repotting my Salvia plant soon, but since I need to keep it indoors for winter and space is limited, I'm thinking of burying most of the stem under the new soil to make the plant shorter. Would this cause any problems? Alternatively, I'm considering a hydroponic approach where I leave the plant in its current pot and let the roots protruding from the bottom reach into a reservoir of tap water. I would add nutrients to the soil on top, which would be moistened to facilitate nutrient absorption while the water reservoir allows for root expansion and water uptake.