I wouldn't give that one to you for the duration of the fight, maybe at the outset though.

I wouldn't allow it. You have to actually be in melee to be a friend in melee. The double is just mimicking your moves, it's not actually in the fight.

If the opponent didn't actually see you make the image, you could suprise him on the first attack as he finds out which is real?

The one that's actually attacking or defending as opposed to moving his limbs blindly in the air nowhere near his opponent? I can't imagine it being difficult.

It's a dumb, unintelligent illusion standing right next to you doing exactly what you're doing. If you reach out to flip a light switch, it's reaching out to flip a light switch even though it's a full meter or more away from the light switch.

Tangent, I allow the image to be a distance away set by the caster so long as the subject and image location are both in the field of view. I also allow the image to remain in one spot (though it continues to mimic) while the subject goes on if the caster chooses to cast it that way. Best, because the subject is not targeted by the spell, it can be cast without their knowledge.

While useful to Private Detectives and Peeping Toms, it is also great for the god complex NPCs to have a living chess board of their pawns.

If the image ran straight at an opponent, while the caster ran beside it, the opponent is likely to block the first melee attack from the image. I would give the caster the "friend in melee" bonus on the first attack if the opponent didn't realize the image was an illusion spell.

I think it's reasonable to give maybe a -1 bonus for the first attack with this. It's clever and not too powerful.

It wouldn't be a friends-in-melee bonus, though, just a GM-thinks-it's-cool bonus that only works on people without astral perception, ultrasound, foreknowledge of your penchant for fakery, etc.