Sorry, I don't think that is possible.
Good idea though, could have some interesting applications. I'd use it to select what type of government my race has, with different bonuses and penalties as seen in Galactic Civilisations.
Actually, you can, though only with using legacy code. At one time you were supposed to choose your loyalist/rebel faction in the game and this choice would unlock your faction's unique techs while locking those of the others. It is kind of difficult to describe so I'll just point you to the Sins of a Galactic Empire mod which uses it to let players pick between two types of titans.
However, I will warn you that this system was really designed for the player making only one choice. It gets really tedious to use if you have multiple mutually exclusive techs (I.e. you can pick tech A or tech B and tech C or tech D).
