Hi,
We are saying that there is a patch in progress for Centreon 2.4 that will allow 'hard coded' parameter, and so use new shinken parameter like criticity or escalations easily. But don't exect a full Shinken support from now, it's still not fully integrated in Centreon.
By the way, mixing Nagios and Shinken in the same Centreon can be a problem I think. You can have problem with mixing data in database (nagios overwrite Shinekn tables, so Nagios should be start before Shinken, always).