Just to update on this example if you define a $GAIA_DISTRIBUTION_DIR then all apps would be expected to come from that directory path.  
If however you want to refer to a specific directory in your config file you can list : 
{ 
  ["/var/gaia/apps/browser",... 
   .... 
   ]
}
The assumption would be that you would provide either the relative or absolute file path.  

It might be more convoluted for someone to understand that they have to maintain a name of the app directory in the config file, which is not necessarily the same as the "app name", and then make sure the APPDIR_PATH is well populated to find the aforementioned app.  

I am open to a concept like this, but then i think we should define the APPDIR_PATH inside the config file & ENV variable or something of that nature?  
Generally would like to make it extremely clear what the thought process is, otherwise i can see it being a bit confusing