Whats wrong with Cubase stereo delay?
I don’t know if any plugin is going to generate any sort of difference information thats gonna be any more interesting than copying detuning, pan, etc.
Otherwise you’re going towards chorus and that sort of stuff.
What exactly did you have in mind? You want difference information created from a mono source. What do you want Cubase to do? Do you really want Cubase to do it for you?
*Not that I haven’t thought of it before too.