Is the ISS in a suitable orbit and of a suitable construction for use as a staging platform for future space missions, or is it optimized for some other other purpose, such as easy access or scientific research? I can imagine a lot of factors have to be considered when designing a space station, depending on its mission and the state of the technology. and I wonder if the ISS was an attempt to come up with an optimal solution for a specific application or a good compromise for a variety of uses. I'm just curious as to what is was primarily designed to do and its function.

It's pretty clear now the Space Shuttle has not fully satisfied any of the stakeholders in the space community, and I assumed it was because it was made too general to do any one specific mission well. But I also recognize that with big expensive systems like this, you can't make things too specialized or too generalized, you have to find a balance that will be as useful as possible to everyone, as well as meeting political and budget objectives. These seem to be policy, not engineering decisions. It may also explain why our robot probes seem to be so much more productive than our manned missions. They can be optimized for their missions.