The settings file you pass in the command line via "--settings" is always prefixed with the settings directory path (i.e. it is not supposed to be a full path, but just a filename).
Simply use:
Or, if you want the viewer to use /home/mich/.coolvl/ instead of /home/mich/.secondlife/ for its files:
But with Linux, they are many more options, such as using symbolic links... Or even using a full custom wrapper script in ~/.secondlife/cool_vl_viewer.conf ...