Adding an island can be a complicated and expensive endeavor. Will the cabinets and countertops match the ones in the rest of your kitchen? Or will they contrast? Are you going to drill through the floor for water and wiring? How much money is in the checking account?
Far simpler and cheaper: Buying an island. Go to your local restaurant supply store. Buy a stainless steel prep table (they come in a variety of lengths). Open the box, assemble (the only tool you’ll need is a screwdriver or an allen wrench), and put your new island wherever you want.