Battle Rifle is a great choice, of course. Magnum too, even though i'm curious about the Bolt shot.
Thruster Pack looks great if you want to close the distance really fast and makes much more sense for a spartan than evade did.
Shielding is good if you want to get back in the action faster after a gunfight and Fast-Track is of course great to rise up in the ranks quicker to get that Specialization.
Dexterity is a good choice too, especially together with the thruster pack and magnum, because the magnum will do more damage up close, so if you can get close really fast and then switch to the magnum fast too, that's pretty lethal.
Explosives looks like a great choice on smaller maps where nades are more likely to hit you. So i'd probably say Dexterity on bigger maps and Explosives on the smaller ones.
My choice will probably be this:
Primary: Battle Rifle
Secondary: Magnum or Bolt Shot.
Grenades: Plasma
Armor Abilities: Promethean Vision
Tactical Package: Shielding
Support Upgrade: Sensor
That's my plan as of right now. I'm sure i'll do a lot of tweaking though when the game is released