OP, if you’re looking for the absolute most easy build for your friend to play then it’d be Forcewave Warlord. Answering your list of reasons:
1 - Forcewave is a simple skill to use and very intuitive.
2 - The only main skills are Forcewave, Blitz for movement, and War Cry when you’re stuck in. All the other skills are passives that increase your power/toughness without need to activate them.
3 - The damage and AoE are very good even before you get the MI two hander.
Honestly, if you do have him play it your biggest concern will be making sure he doesn’t get bored of it. It’s well known as the easiest way to level a soldier build for a reason. The link below has a good progress guide for leveling with Forcewave.