As regards to planet colonization, I have an idea which, unfortunately, probably wouldn't, or couldn't be implemented until GalCiv III. Each race would have attributes for each type of planet - terran, barren etc. Though research, you could increase your race's attributes - for instance, +3 to barren and so on. The planets themselves would have a type (terran, barren, toxic etc) and a basic class number which could be anything from (say) -30 to +10.

The way a race sees a planet, the basic planet class is added to the race's attribute for the planet's type. If the result is below 0 then, for that race, it is a uncolonisable class 0 planet, otherwise, the class is whatever the added result is.

ie: A planet is generated as basic class of 5 and toxic. Most races begin with about -15 toxic attribute. Since the resulting sum of -15 + 5 = -10, they will see it as a class 0 planet. However, one race has the toxic attribute of 0 thus sees it as a class 5 planet and can colonise it, but with little room to move. Another race excels in living in toxic waste and with a +10 attribute to toxic see it as a 10+5=15 class and so will thrive on it.

Under such a system, I can see great flexibility in race starting attributes for different planet types, meaning that they each see the planets quite differently in terms of potential colonisation to begin with. This also puts an end to the class 0 wastes of space. One race's waste of space is another race's gold mine.

The thing in researching to colonise a planet is you may not know how much to research before you begin to see beyond a class 0 for it. Perhaps with an advanced scanner from later down the tech tree, you can see the actual negative number rather than just a 0.

But I think the idea has great potential. The current couple of levels of research for each planet type seems rather artificial and a bit shallow.