I wouldn't agree with completely separating ground and space trait choices - removes the choice to specialise in either.
But maybe if each race has a unique trait that affects both space and ground, then picking 1 space trait, 1 ground trait and the last option entirely open.
As for offensive vs defensive - to me defensive ground traits are only good early on since when u have decent armour the diminishing returns get u, but offensive traits are mostly unaffected apart from armour that boosts attack damage a small amount. (Even then extra expose chance or exploit damage is more appealling)
Yes space abilities would be interesting maybe if only available to specific careers otherwise it might reduce the differences between the careers.