With log stash you should be able to enter something such as:
logstash_config="/usr/local/etc/logstash/*.conf" 

which is able to import all *.conf config files, the current startup script in /usr/local/etc/rc.d needs to be modified to allow this, otherwise you get multiple errors about each file being an invalid command line option

modify:
/usr/local/etc/rc.d/logstash, line 85:
logstash_args="-f ${logstash_config} ${logstash_log_options} ${logstash_opts}"

to:
logstash_args="-f \"${logstash_config}\" ${logstash_log_options} ${logstash_opts}"

resolves this issue.