Whoah, someone's actually doing what i'm searching for? Nice. Wasn't really keen on starting my own mod just to make the career mode somewhat playable. I'd prefer a tech tree that does not require any additional mods though (everything needed to play should be available in one pack, i think). Perhaps you should just focus on making the tree to make more sense, and reduce the importance of historical-like progression? Not sure a "period of sub-orbital" flight really works in KSP, not as there's a limited amount of things to do on Kerbin. BTW, my own ideas included having a Probe core in the starting tech but deliberately no batteries or solar panels. This way, you could use a probe core to test out crazy things without endangering your kerbals but it'd also limit them quite heavily as you need a liquid-fuel rocket to provide them with constant power. However, I think merely fixing the tech tree doesn't really solve the problems of KSP career, it is fundamentally a hodgepodge of elements and the moment, elements whose interaction is rather limited, i think. And there are issues like "What do with science once you have researched everything?", and the fact each career is largely identical as it is (on paper, IMO, anyway, not sure what others think).