I assume you want this instead of:
-'Edit reply' to the invite "This time works better for me", then the person has to confer, adjust, etc.
-You going to the calendar and creating a "Could we move this meeting here?" invite.
ie: You want an another button under tentive called 'suggest time/date' that would notify the creator (so they can accept/decline the change) or even insert "User __ would perfer x time/date" into the notes portion of the sharer's calendar event itself if you have manager rights.
Don't see an RFE open on it, go ahead and file it in
bugzilla.