Loki would pose a bigger threat and he still wanted to recruit him
Also we don’t know what gunkos eyes even do to begin with
I think you're misunderstanding
I don't think it would make sense for Gunko's eye powers to be something that allow her to break control from Imu, because he would be going out of his way to recruit a liability.
Loki wouldn't be a liability, because if he became a HK he wouldn't be able to control himself at all, Imu could influence him.
Basically, Gunko should, based on what we know, remain "evil" until Imu's defeat.