I've been working my way through options to try not to do what you've suggested but I've not been able to find an alternative that works.
MakeFeatureLayer doesn't appear to support Schematic Datasets and gives an error using arcpy.
You can't update the data source on a Schematic Dataset using arcpy tools. Top note in the 'known limitations' section.
Updating and fixing data sources with arcpy.mapping—Help | ArcGIS for Desktop
I've been considering trying to make one schematic that I keep overwriting so that I only need one mxd, or having 1000 mxd files but those sound terrible and painful.
I'm going to implement the idea you mentioned above. I'm going to export my schematic to a temporary geodatabase and use that to create a grid on top of, generate my pdf series for that schematic #with Data Driven pages, then move on to the next schematic.
schematics ddp data driven pages