I've had the same question!
The PID for the default log files are random and cannot be predicted, so it's impossible to include in your source code package a sling:OsgiConfig node that overrides this settings in any target deployment environment.
The <identifier> is an alias for the "actual" ID (the machine-generated random one). This is the pattern when configuring service instances that a factory generates.
The Sling docs mention this (see the TODO note on http://sling.apache.org/site/jcr-installer-provider.html)
However, I believe you can continue to reference the service instance using the <identifier>. Have you tried?
Yes, I've tried like this:
but with no success. I mean, the config dialog is opened with no properties at all.