You would also need more delat-v or a tug to get Dragon to Moon and back. Unlike Orian (or Apollo back then) Dragon actually does not have a real service module - the trunk provides aerodynamic stability at abort and hosts solar panels and radiators - but is otherwise empty.

For lunar operations you might need to put fuel tanks inside the trunk & the make the fuel usable to the thrusters in the capsule.

Or alternatively put some simple thrusters in/on the trunk. These could have more efficient nozzle compared to what Dracos & Super Dracos have due to capsule aerodynamics constraints (compare the nozzle bell size for Orion and Apollo). On the other hand this would increase complexity quite a bit & you are effectively lugging around duplicate engines.