The main goal of the research system as I see it is to provide a different set of technologies researchable each game.  Currently it does this by being pseudo random, and tieing the amount of research points to the category (civic, warefare, etc) level, rather than particular technologies within the categories.

The Problem: after a few levels in any particular category, there are too many techs that may appear when you research the field.  This causes a cat and mouse game with some earlier techs if you decide you want to hold of on them to get a rare tech.

My Solution: Use a magic the gathering style cards in hand limitation, AND reduce the  number of techs appearing each level.  Basically each time you research a category, you get a list of techs that were in your "hand" from the previous breakthrough in the category, plus 1-3 random new techs that haven't appeared before.  There is a limiter for each category of how many technologies you can keep in your hand after each break through.  After you choose the technology you want to get, if your "hand" holds more technologies than what that category is allowed, YOU must choose which technologies to NEVER research.

I believe this would put an end to the issue of the cat and mouse of technology discovery and make create a strategic choice for the player to CHOOSE where they want to go with the category.

NB//  I'm wholly against the use of prerequisites in the technology fields.  But if they are there, then the UI needs to be designed so that all techs that have a technology in your "hand"  as a prerequisite can be pulled up to enable the player to make informed decisions about whether to reseach the tech or not.