When loading rasters into a Mosaic Dataset, it should be possible to specify an environment variable as part of the path to the data to alias the server name or server with a share name. This way, the data can be migrated without having to alter all the paths stored in fields. Also, in tests the value could be set to a path on the test server and in production to the name of the production server. The client (e.g. ArcGIS Server, ArcGIS Desktop) would substitute the variable to insert the name of the correct server.
This has been available for unmanaged raster catalogs and hotlink fields and is very convenient. For example, an environment variable "SharedData" may be defined on client workstations, and paths in raster catalogs or hotlink fields may be something like "$SharedData\Raster\Img0815" or "$SharedData\LinkedFiles\Report.pdf", where "$" indicates an environment variable defined at the operating system level of the client machine. Actually under Windows, the "%" notation is common ("%SharedData%"), but ArcGIS Desktop supports the "$" notation.
However, the Mosaic Dataset does not currently support environment variables in the path to the data. There has been a request for this, logged as NIM-073165 "Provide a way to change paths to raster datasets in a mosaic dataset without modifying the mosaic dataset properties or configuration", but it has been rejected "as designed".