From the announcement:
Many of you have asked for an easy way to just get everything for a single faction so here is the complete add-on package that when combined with an army deal leaves nothing out.
Because the list of add-on units varies for each faction there are three different deals for both primed and premium. Given we are soon to unlock the free body/legs add-on I have also included the fourth body so every pair of arms you have coming can be fielded as a stand alone unit.
All you have to do is up your pledge by the Special Bundle Price shown for either primed or premium and at the pledge manager stage tick the all-in option for your faction. These deals have some extra discount in them and as such they are fixed, just like the army deals, and cannot be split up. You can of course still add other items to your list.