Looking quickly at the code, I’m not actually sure if Wirebox even uses the modelsExternalLocation setting. It’s only referenced in the legacy bean factory code.
Set up your external folder as a scan location in your binder config in /config/wirebox.cfc.
// Package scan locations
scanLocations = [‘sharedstuff.model’],
Now, if you reference a model named “foobar.BarService”, it will be looked for in “sharedstuff.model.foobar.BarService”.