Write an EEM script that looks for your syslog message at level 6 and in response emits a syslog message at log 5 or better.
Note: I don't know if this works on your device/IOS version.
The following example "converts" a level 5 syslog (the "%SYS-5-CONFIG_I" log you see when you make config changes and exit the config mode) to a level 2 syslog. Note the regex which grabs certain fields from the original syslog and renders them as is in the new syslog:
Switch#sh run | sec event manager
event manager applet logConfigsAtLevel2
event syslog pattern "^.*%SYS-5-CONFIG_I.*$"
action 10 regexp "^.*%SYS-5-CONFIG_I.*from (.*) by (.*)$" "$_syslog_msg" match who where
action 20 if $_regexp_result eq "1"
action 30 syslog priority critical msg "somebody ($who) from ($where) is up to no good" facility "EEM"
action 40 end
This results in:
*Nov 22 11:13:44.409: %SYS-5-CONFIG_I: Configured from console by console
*Nov 22 11:13:44.415: %EEM-2-LOG: logConfigsAtLevel2: somebody (console) from (console) is up to no good