For me it sounds like a very good idea!
I've posted this issue a few weeks ago in bug forum, but it's wad.
I find this a bit silly that you can get a L2 tech through tech spread, though you don't anything about L1 tech.
On the other hand i don't know how much effect this have on game balance, because you will not be able to research all techs in vanilla 1.02 during a normal 1066 game (and adding prerequisites will slow down tech resesarch).