[MattII]

Well the per-turn change would be small, but I couldn't give you an exact figure, because the number of ways you could change the characteristics could possibly be pretty huge, I suspect you'd have to standardise the costs first (Aggressiveness, Defensiveness and maintenance all cost 50 points/level in SE4, as compared to 25 points/level for the others).

Oh, and just a minor bit of flavouring, I'd like to see you able you get to set the 'age' of your race both in years (the years number you see at the top of the screen at the start of the game), and in months (how many turns it takes to pass a year, anything over 10 would have nonsense symbols, or highly stylised letters).