Oh and there's one more thing. What if Imu is able to control Gunko in such specific way because he locked/whipped out her memory? After all people who don't remember who they are and also don't remember their past are very easy to manipulate. So, I started to wonder if Imu could completly lose her if only she regain her true identity. Seem possible because Imu looked pretty paniced when he realised she's getting her memories back.
I don't think Imu can wipe or read memories because he didn't know Saturn secretly transported Emeth out of Mariejoa to be studied.
He even asked if Gunko remembered something, so it indicates he can't tell what she is thinking.
Imu can only control people physically, but he can't manipulate thoughts by the looks of things.
If Imu could read minds, he'd have known that Loki was the one who killed Harald as well.
He just communicates telephatically, and can control the body via instructions, but nothing beyond that by the looks of things.
If he could read minds too.. he'd simply have to take over Roger's body while he was alive in order to find out where the One Piece was, and the problem of One Piece would have been solved.