engine | Add templating to manage dynamic option in policy

Hello,

Could it possible to use templating to define the option parameter (json object) of an engine policy ?
I would like to set a relative time for owl_leaks : "from_date":"2010-01-01", "since":"2017-01-01"

Sidecar Collector configuration in Graylog, could be a starting point (example) in using runtime variable and other variable in order to produce a dynamic configuration file.