I've built a workaround in the SAS Spindown plugin, when latter is installed in versions 6.7-6.8. The workaround is complex and rather involved, to make sure it's "safe" even if the user reconfigures the syslog settings in the webGui (e.g. includes a background process that waits on modifications to syslog.conf and, when triggered, reconfigures the filters). While it's done and working quite elegantly, I'd not recommend going that path.
This is really quite broken right now, so if it can be fixed in 6.9 it would be great.