That same objection can be raised against technocratic control of monetary policy as well, and in fact, people argued against creating the Fed for exactly this

That same objection can be raised against technocratic control of monetary policy as well, and in fact, people argued against creating the Fed for exactly this reason. So what makes fiscal policy so special that we need to keep it out of the Fed's hands? Monetary and fiscal policy are the two main levers that the government has over the economy, but only giving one of them to the Fed means that the Fed has its hands tied in many circumstances (like today, when rates are persistently low), and requires the Fed to constantly guess what Congress will do and react to it. Anyway, to answer your question, the Fed would exercise fiscal policy with the same aims and goals by which it uses monetary policy.