Does anyone know if there is any public documentation on how to create these?
Take a look at this ESRI technical paper "Customizing ArcGIS 10 locators" http://www.arcgis.com/home/item.html?id=aeb00de638f3492a93308a4a03183c7d
You can create your own composite address locators.
(Might be easier to modify an existing one to start with)
The maximum number of participating address locators in a composite locator is 30, but it is recommended not to use more than 10, otherwise geocoding may be significantly slower.
Commonly used address locator styles http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00250000000v000000.htm
9.3.1 but can be used with ArcGIS 10
"They can be used to create locators with ArcGIS 10. The locators can then be used for geocoding at ArcGIS 9.3x or 10."
Migrating address locators created with ArcGIS prior to version 10 http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Migrating_address_locators_created_with_ArcGIS_prior_to_version_10/00250000001w000000/
You also might want to look into the Geocoding Development Kit.
Even though this KB article was last updated June 2010, there is no mention of it being used with ArcGIS 10.0.