I have an Ibanez GRG170DX. It has a floating termolo and a non locking nut, I want to lock it so, it wouldn't go out of tune every time I do something with it. Instead of buying a floyd rose and installing it, I was thinking of buying a Ibanez RG series neck with a locking nut allready installed. Then I'd just screw the new neck to my GRG and use the locking nut with the floating termolo as it was a floyd rose bridge.
I don't think having a locking nut is going to help tuning stability very much to be honest. What it will mean though is that when it does go out of tune, you'll have to unlock it.
The Ibanez GRG170DX bridge does not have fine tuners so you cannot use a locking nut with it as the guitar would be out of tune when locked.