yes you can play sandbox games and there's many parameters to tweak like :

number of planets, number of habitable planets, number of stars, stars distribution, size of map, technology rate.... and much more like being able to customize your opponents

and if that's not enough, the game is moddable although a few parameters are still hardcoded

So I take it the tech rate change mid game ended up not coming to fruitation?  I remember Brad was working on something of the like, but I think there was enough opposition of taking advantage of the AI and moving it just when you wanted to move it.