Hi Phil...

Any thoughts on the best way of doing this...
This is not a request, just an insight into how people maybe using exiftool.

Aliases are useful for returning a group of values.....

However, another use of them is to check several equivalent locations for metadata.
You maybe looking for one value but it may be defined in several places...
Using the aliases you can define an order of precedence...
e.g Look in EXIF, then in XMP, then in PhotoShop for Resolution.

A problem is that the locations returned by aliases "may" not use any common string which enables us to associate
the value returned with the specified alias. As such we have to call exiftool several times, once for each alias, filter the results,
ignoring everything but the first returned value.
If we had a command line which used three aliases to return three possible values we will get a list of assorted locations/values returned
which then need to be parsed. We need to know what locations map to which aliases in the ExifTool_config to parse these values.
Only then can we match the values returned with the aliases....

There are two possible enhancements here...
1. Use aliases to return a single value from a list of possible locations
2. Be able to use multiple aliases in a single invocation and identify the values returned without
knowing the contents of ExifTool_config

Hope this makes some sort of sense....