You will be offered MK5 shields shortly after arriving in OL, rather than MK3 shields which have been available since arriving in DeVries.
MK2 weapons will become available after you are offered upgrades during the Xenon invasion.
MK5 equipment will become available after completing chapter 3.
MK2 weapons will become available after you are offered upgrades during the Xenon invasion.
MK5 equipment will become available after completing chapter 3.