The best place for the tank is below the orbiter just above the engines.
This placement allows short and straight pipes from the tanks to the engines. All parts could be balanced and aligned. No heavy gimbaling necessary. Solid fuel boosters could be aligned parallel to the tank. Separation of the tank from the orbiter is as easy as a conventional stage separation.
The engines are not needed in orbit and for reentry, but they could not be recovered easily.
This placement was used for the never realized spacecraft Hermes.
Your placement of the tank above the nose of the orbiter requires too long and bend pipes. The heat shield at the nose of the orbiter is not a good place to connect the pipes and struts to the tank.
But the liquid cryogenic engines of the Shuttle should be recovered with the orbiter itself, so the tank could not be placed directly above the engines.