This idea is based on the assumption that Centeon snmp plugin does not read snmpv3 options unless you specify it in the command.

See code for centreon::plugins::snmp

if ($options{option_results}->{snmp_version} eq '3') {
   ...]
}

Here my idea:

1. Create in the engine, and wherever it’s needed, all the snmpv3 ad-hoc host macro, empty by default, like $_HOSTV3AUTHPROTOCOL$, $_HOSTV3PRIVPASSPHRASE$, etc.
2. Change the CMD in the packs, so they have by default all the v3 parameters, populated with the proper, for now empty, host macro.
3. Configure the web interface to show snmpv3 field to populate, if you choose ‘3’ as snmp version