To access your map document and be able to export it out, you would need to use the arcpy.mapping module.
It is fairly easy to export out your data view and set a scale for the dataframe, I guess my question would be do you have a kml for each tile, or are they one large dataset? If they are a large dataset, you would need to probably make an index(grid) shapefile and you could have the script loop over each box in the grid zoom to it then export out the data view.
If you are still needing help with this, if you could give a little more info, and the workflow you are needing, that would be great. I have a similar script for something like this where some of my co-workers need georeferenced imagery for autocad with arcgis layers saved to the dataview and they select the polygon they need by the ID number, I could give you a good starter script to work off of.