I have an idea. Before you can do anything like that, you need to make a multi block rocket assembler, which you can build and customise your rocket. When you build a basic rocket, it appears in the multi block structure. At any point you can take the rocket out with all its upgrades thus far and put any rocket back in. Upgrades work by improving different modules to get new stuff. There could be different modules including, but not limited to, rocket thrusters (improves the ships fuel efficiency as it is upgraded), fuel tank (more fuel stored in the rocket), cargo bay (more items stored in the rocket, could also store the landers and space stations), crew capsule (allows multiple people per rocket), guidance program (allows you to zero in on specific coordinates) and optional improvements to the lander.