The weapons and related research is somewhat static and known before the game begins--we all know what lays at the end of the rainbow. The developers apparently try to randomize this a little with the luck, research bonuses, etc.
1. Suggestion re weapons/defenses: We're basically rock/scissor/paper. How about a fourth weapon and/or defense type that behaves just like the other three?
Would that add anything other complexity or just make it incredibly difficult when all the races are in play and have developed all four types? Perhaps as an option? What if the fourth weapon type was incredibly hard/expensive to research but had no natural defense? Similarly, what if a defense was difficult to acquire, but had no natural weakness and was equally and highly effective against the normal types?
I'm assuming this is a non-starter suggestion unless implemented as a module that heavily bonuses the other three types (either defense or attack.)
2. Suggestion affecting research choices: During game setup, have options to randomly (or specifically) skew one or more weapon and/or defense types either above or below the normal game setting. If done randomly, you wouldn't be absolutely sure that the research path you were on was going to lead to the Holy Hand Grenade. Seems like this would be relatively easy to implement and if optional could make the game interesting again.