I never have trouble adding techs or units but my tech tree looks like a mess and my units all look alike since I don't know how to make 100 different unique animations for all my new units.
Whatever I type as the civilopedia entry is what the unit looks like in the game, so I can't use the other icons in the game, like the Zero in the WWII Pacific scenario, looks like a regular fighter, because I have to type PRTO_Fighter for the Zero in my own scenarios, you know? If I knew how to make all the unique units and such look different I'd be very happy, the techs and even unique buildings are of secondary concern.