Necessary to have properties which could be evaluated dynamically in time of configuration file read.
Currently we have statical defined property values (by property tag or files) or we could get properties from System properties.

In version 0.9.17 was made possibility to save formatted timestamp in property.
May be possible to create property evaluator tag, to define some properties value dynamically?
Something like this:

<property name="hostName" evaluator="a.b.c.HostPropertyEvaluator">
<parameter name="host_type">ip</parameter>
</property>

Evaluator will be called on property initialization with listed parameters.