I'm wondering if we'll be able to choose our character's personality. I mean, will the cutscene be purely scripted? How will he act? Will some characters be eager and impatient? Will some be gritty and battle-hardened? Bad egg with a heart of gold? Humorous but serious when needed? Who will be a natural born leader? Who will act the squad commander? I'm wondering how it will work.

Hmm... good question, I wouldn't exactly know you may want to check with the compendium, but I think its gonna be scripted with our character just being there and being a background character in some scenes, and the main person talking in others. But thats just me guessing, I'll check the compendium.

From what I heard last if your playing by yourself you will be the Squad commander in the cutscenes. Probably scripted to some degree.

There are characters with different personalities, afaik.

However, the game will put player characters into positions randomly (except for the person who is "hosting" their campaign); so you'll end up with a different character/personality most of the time.