Go to page One of this thread where Plotinus describes how to create a scenario. There is a section about techs that might help. You will need to create a new tech image and use the editor to link everything. So that each 'Civ' could create its own unique units I created a separate 'tech tree' for each of the different protagonists in my Conquest scenario 'Defeat Into Victory' i.e.: Only Japan could create the Aichi M6A Seiran torpedo bomber because only Japan could research the tech 'Bushido'.