First note, is that I DO NOT think the races should be balanced. One of the great aspects of the game is how the difficulty and required strategy change depending on which opponents were in the game. Also, the jump in difficulty from "hard" to "impossible" was pretty extreme. The fact that playing Bulrathi or Mrrshans on "hard" was nearly same difficulty as playing Psilons or Klackons on "impossible" reduced the difficulty gap.
That being said, just for fun, I came up with some changes that I think would better balance the races. For all changes, I tried to keep with the “theme” of the race and to design the changes to further strengthen the bonus that the races already have.
Alkari – +1 to all range
Military bonus are just not very strong in the game. This change gives Alkari a unique advantage in expanding faster to hopefully stay on-par with other races. Then they can get to a place where they can actually apply their military bonus.
Bulrathi –Transports have 200% more armor (hit points). Ships have 50% more armor.
Bulrathi are one of the weakest races because they never get into a position to actually take advantage of their ground combat bonus. The transport change will potentially allow an invasion even with an enemy hostile fleet over the planet. Also I feel a ship combat bonus (different than the other two combat races) is also needed since they are really just that weak now.
Darlocks – Improve starting relations with other races to “wary” instead of “unease”. If a spy rolls 115+, it gets double the effect (like it steals two techs)
The Darlocks often just lose because everyone hates them and then goes to war with them, which this change should help with. Also make their spying bonus even stronger.
Humans – The 25% trade bonus is also gained by the human's trading partner.
Humans are a strong race, so this change is a slight nerf by giving just a little extra BCs to everyone else in the game with the humans. In fact, this might actually end up being a buff for humans because other races will be even more likely to enter trades with them.
Klackons – Cap the double production for worker bonus at the planet's max population. In other words if a planets max population is 100, Klackon workers can never produce more than what 100 normal workers could.
Klackons are the strongest human controlled race. Their benefit is insanely strong early game, and it even continues into the mid and late game. This change keeps their early game bonus nearly as strong when everyone has half empty planets, but it scale down to zero by late game.
Meklars – Change their construction tech rating to “Good”.
Meklars bonus is strong late game, but it can almost be a no-advantage in the early game and mid game. You often find yourself at war and need to stop factory production before you can build your bonus factories. Or even if you finish your bonus factories, you can be spending nearly 50% of your planets production on just cleaning up your factory's mess. This situation is common because Meklars are “Poor” in Planetology tech, and they frequently don't get offered “Eco Restoration". This change would open up those “Improved Industrial Tech” and/or “Reduced Industrial Waste” techs.
Mrrshan – Weapons on ships have no construction cost. Also there is no ship maintenance costs.
The Mrrshan AI is by far the worst in the game because it tends to build and maintain HUGE fleets, which basically grinds their research to a halt. This change will allow them to build their fleet for slightly cheaper and then not choke on the huge maintenance costs. This change lets the Mrrshans actually build a fleet and take advantage of their racial bonus without going bankrupt.
Psilons – Remove their “Good” tech rating on all techs. However, increase the selection of techs available to research by 50%.
Psilons are by far the most powerful AI controlled race (some would also argue the most powerful human controlled race, although I would argue the Klackons are). Psilons already have a 50% bonus to all tech, and the “Good” rating gives them another 25% bonus on top of that! This change takes away the additional 25% bonus. Instead, it gives them more of a MOO2 type of tech advantage any allowing them more options on which techs to research.
Sakkra – No changes
They are the very definition of the average race. Their bonus is strongest in the early game, but it can still be relevant all game long (such as when you need to rebuild population after invading).
Silicoids – Atmospheric terraforming and soil enrichment can be researched. They still wouldn’t get the growth bonus but their planets get the population max bonuses.
Silicoids are easily the strongest early game race by ignoring pollution and colonizing any planet. However, they almost always dwindle by late game after the other races have controlled environment and waste reduction tech . This change would help them stay competitive into the late game. The fact that you can’t do this already is almost silly. I mean you get the benefit from planets that the AI converted before you take them over.