I'm confused at what you're asking for. The Step and Repeat function is perfect--and quick--at what you need to accomplish, so I can't understand what you mean when you say "set up that you would like to avoid".
Also, if there are "objects" you are trying to duplicate, why do you use mail merge? That's for changing text information.
If you're looking for a "one-button" solution, the closest you'll come is the step and repeat. If each individual object changes each time it is duplicated, that sounds tedious any way you look at it. Give us some more info (or even a diagram/sample) on what you're attempting.