Space Transportation Replacement Set (STRS)
STRS is mostly just a concept at this stage, and likely will remain that way as long as other major projects remain on my plate (so in other words, forever! :P)
Obviously the basic idea is OpenTTD in space on some sort of planet or moon or asteroid or something with the landscape being replaced with a crater-filled rock, while water is replaced with empty space. Land vehicles would operate mostly the same, while aircraft and ships would end up turning into different kinds of spacehips meant to traverse the empty space between worlds. Ships would serve as the slow freighters while aircraft could act as the high-speed interplanetary transport.
This idea is definitely not new, in fact a similar set has actually been created at least once, however no release was ever made public, or at least it hasn't survived the test of time. Regardless, I find it a very interesting idea, even as a simple graphical replacemant it offers a big change to the feel of the game. If taken a step further and made into a complete gameplay replacement similar to Wasteland, the possibilities are almost endless. Someday my hope is to get caught up enough in my other projects to take this on more seriously, but for now the idea is always open for someone else to take on!