There's a couple of different issues with the ISS. one - it's at an altitude that needs regular boosting or else it would reenter. Not a big deal, but annoying that you need to add thrust to keep it at a low orbit, versus putting it out to say 1500km or 2000km alt and it could stay for centuries with no boosting. Second... the inclination of the ISS is not ideal to launch to the moon or the planets due to the plane change needed. It would be much better if the orbital apogee (highest point) were on a nodal point with the planets, and as high as possible, to minimize the Delta-V to exit the base on the right plane and trajectory.