The autonag bot relaxes the severity, and then comes back a week later to ask for the severity to be increased

I've seen this happen a couple times; latest instance is https://bugzilla.mozilla.org/show_bug.cgi?id=1403656

• The bug's severity was initially S2 for this bug, which is a fuzzblocker, and which happens to have a crash signature associated with it, and have an attached testcase which reliably triggers the crash.

• 6 days ago, the autonag bot downgraded the severity from S2 to S3, with the following comment:

Since the crash volume is low (less than 5 per week), the severity is downgraded to S3. Feel free to change it back if you think the bug is still critical.

For more information, please visit auto_nag documentation.
Severity: S2 → S3

• Today, the autonag bot came back with concerns about S3 being not severe enough, and asked us to increase the severity, with a needinfo nag and the following comment:

This bug prevents fuzzing from making progress; however, it has low severity. It is important for fuzz blocker bugs to be addressed in a timely manner (see here why?).

Can we make the autonag bot do this assessment up-front so that it doesn't cause this sort of back and forth?