@alexal and @blaszkam it would be possible if you install a SASFoundation per SAS/SHARE server you run. You can individually tweak the sasauth.conf per SAS/SHARE server that way. That would probably be too much administration overhead to do in practice though.
@blaszkam what is the use case you have here for needing multiple sasauth.conf configurations?
EDIT: Thought of another method that uses even more duct tape. The sasauth processes parses the configuration file on startup only. You can rotate around the different configuration files as you boot each SAS/SHARE instance up with sasauth.conf pointed at a different configuration.