Interesting. While recognizing it's not a high priority, I'm hoping that the tree for the various mods is as well thought-out as possible, especially the advanced ones like Kethane and Interstellar, so that progression can be slow (like a mission or two per node even in the late game) and rewarding. I suppose this might not be completely possible; in my last career I ended up with over 13000 science on a single mission to Jool and its moons, which finished the tech tree with several thousand left over. The more nodes there are at the end the better, as far as I'm concerned. Especially since the interstellar stuff has great potential for allowing new kinds of science missions, it'd be a shame if it didn't take more than a mission or two to unlock everything.