I'd start with rewriting everything in ancient Sumerian to remove language bias. Ok no... that's just dumb. We should use Esperanto

Jokes aside:
I don't think there's much that should be changed. They definitely could use rewriting for clarity. Supposedly they were written by English native speaker but...
If I was to change something by Fiat/handwavium then stuff like=>
-Far more special keywords and redaction of existing ones. Examples like Totem (nearby rally bonus) or Stable Platform (weapon doesn't havealty on double shooting). RA and IS should have the (re)roll value specified on the ability. eg IS(5+)
-D10 or 12's. Resign the d6 to the dustbin of history. Dice roll apps are everywhere nowadays.
-douche the aerospace rules. They're terribad. Use a tried a true idea like line strafing (it works)
-Sime type of CC oriented transport rules, like Assault Transport sorta but in epic. Those poor 'zerkers need a boost

-oh and something that actually uses the area effect template that the rulebook hinted would be used in the future.
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