Hm. For starters, it could go fully classless and level-less. Roll class benefits, perks, achievement benefits, and rank benefits together. Divide them into categories, keep skill level requirements or escalating costs as necessary, maybe flag some as unavailable (or only available) at character creation, but present them all in the same format, in the same chapter. They're functionally close enough as it is.
Detail and explain the spectrum between light power armor and body tanks all the way up to full size mecha, and include some flexible creation and piloting rules.
Include some stuff explaining damage ranges for weapons, primarily for designing new material. This part always seemed so incredibly arbitrary to me. What exactly does an accuracy bonus represent, as compared to a steep gradient between ordinary and amazing damage results? What about a fairly flat gradient? What's the difference between stepping up to a large amount of wound or an average amount of mortal? If you're doing a series of similar weapons on a scale, how much should you drop the damage stepping up from O to G firepower?
That's just some major things off the top of my head. What it basically comes down to is I'd like to see a bit more of the 3E-style unified design and non-arbitrary underpinnings. And mecha.
