Casper Composer Stripping User Data

There's no need to worry about that. Whatever account gets captured in a Composer snapshot gets used as a wildcard if you use the Fill Existing Users (FEU) or Fill User Template (FUT) options when deploying the package. The one caveat is that you must use a DMG format for this to happen or it will in fact drop the file into the admin folder or whatever path is shown in the package.

If you have a package you'd rather deploy in .pkg format, try splitting these up. Deploy the software as a .pkg and have a separate "settings" DMG file with just the user specific files that rides along with it in the same policy. We do this all the time and it works just fine.

Lastly, you could script something that will copy the file(s) into the current user's folder or other home directories and put it all in a postflight or postinstall script, and then deploy it all in a single .pkg format.