Gold, and precious metals in general, would be the best beneficiaries from such an event, while the US Dollar would be the obvious loser. The stock market would likely go into a bear market on growth fears, while long-term interest rates would increase (the opposite of what Trump wants).
The negative consequences though would stretch to the global economy as a whole. The Federal Reserve is the anchor of the global financial system. The U.S. Treasuries are considered the benchmark “risk-free rate” and almost all global debt is priced as US Treasury rate + risk spread. If long term rates were to increase in the US, they would also influence long-term interest rates of other major economies. The initial reaction would highly likely be chaos and uncertainty in the global financial markets.
The good news is that even if the DOJ were to officially indict Powell for “misleading Congress” or “misuse of funds”, and Trump were to fire Powell “for cause”, the Fed Chair has already signalled that he would fight any removal in court, much like what happened with Fed’s Cook. The ultimate decision would likely rest with the US Supreme Court.
Nevertheless, the initial reaction to the DOJ indictment would be similar to the one we saw today, but bigger in magnitude