First upgrade path (maybe will effect all the explosives or all the artillery or all that):
Improved missiles 1
Cost: 4 Effect: +1 attack to all rocket artilleries
Improved missiles 2
Cost: 5 Effect: +1 attack and +1 range to all rocket artilleries
Improved missiles 3
Cost: 6 Effect: +1 attack, -0.1 accuarcy penalty, +1 range to all rocket artilleries
Second upgrade path:
Imported ground engines 1
Cost: 4 Effect: +1 speed for all ground vehicles
Cost: 5 Effect: +1 speed for all ground vehicles
Cost: 6 Effect +1 speed for all ground vehicles
Thanks to those techs humans will became the masters of mobility and firepower. That would make sense, given humans aim on that from thirty years war and the Gustav Adolph's army model. Additionaly they have best navy, but other races will be able to catch up somehow. Other races can also steal those what gives some extra taste for gameplay (I will make that balanced somehow). Humans won't have too high survivability and not too good melee damage, as well as worse movement of basic infantry and weaker fighter planes to make them balanced, also their psionics will be hard to access and not too strong. They also could steal the techs from other races to negate some of those weaknesses, if I will really balance those techs the game could became preety cool at some point, especially when we have those WMDs here [insert evil laugh here]
