After playing for a while, I've really started to think about the tech tree.  Once you get to the late game and you have researched all the tech you've basically seen all that there is to see.   It would shake things up a bit if the choices you make as you research through the tree locked you out of certain branches.  If balanced correctly it could really spice up the research aspect as you'd really have to think about what to pick next.  It would also color things a bit as your experience playing a particuliar race would differ depending on the choices you made.  I know I shouldn't compare, but just so it is clear I'm thinking in terms of how research worked in Master of Orion or the skill trees in Asheron's Call 2 or Diablo 2.  The tree might need to be fleshed out a bit more for this to work effectively though.

What do the rest of you think about this?  Would it be fun?  Would it be technically feasible?  Has this already been discussed?