Should be entirely more like star wars empire at war.
In fact besides more open planet side rts. It should be almost exactly like it in principal.
No, halo wars 2 should be an exact copy of DoW2, that game was awesome.
no, halo wars 2 should be like halo wars but with more free building, unit balance and better pathing for units.
Imagine if you got to battle in space in halo wars 2 that would be freaking epic 
i keep thinking about this;
what would the space stations look like/ function like?
and how would you make defensive turrets?