something like monit.service.in/monit.upstart.in in contrib
This is too broad and need to be better specified. Please provide a use case, with in and out variants.
use case: something like
instead of hard-coded path.
I assumed you meant something like a chef template (https://github.com/phlipper/chef-monit) or similar to make it easy to duplicate and distribute which seems useful, but also is a broad topic. Simply replacing some example paths during build time is certainly less ambitious but maybe unnecessary since these are just commented out example paths and the users might want to use something else in any case.