I agree. Good post. Without XMLs and the ease of editing EaW would lose a hellavu lost of appeal. I agree that it is only in space skirmish where the game really takes a hit. I think they got the land side of it right. An easy way to get a fairly accurate value of any unit is to basically create a formula and assign values to various characteristics like HPs, damage, range etc. The hardest thing is coming up with a formula and assigning values to special abilities, however once this is done ALL crafts values are derived from this and their cost will reflect their ability so there can be no imbalance. I did this in a XWing Alliance mod I did for EaW and it proved VERY balanced.
btw I was only using Starcraft as an eg of a game with longevity.