The existing option flags should be configurable from sshguard.conf. It's easier and more transparent for end-users when all configuration happens in their conf files. Easier to deploy the same configuration across multiple systems.
The current option flags are:
-a thresh -b thresh:file -i pidfile -p interval (default 120 secs, or 2 minutes) -s interval (default 1800 secs, or 30 minutes) -w address | file
Which should work out to THRESHOLD, TRESHOLD_FILE, PID_FILE, BLOCK_TIME, DETECTION_TIME, and WHITELIST.
Distributions can then ship a customized sshguard.conf for their environments without having to include not-as-easily-configured options in service files (systemd).