Two important considerations
First, we do not yet have Akismet
Second, not many members use the Flag system
For the most part the forum has good Moderator coverage. But there are times when that coverage is a bit thin to say the least. It is during these times that member Flagging is very important in keeping the forum free of SPAM
It has happened on more than one occasion that those members that do Flag reach the max limit.
Currently there are 8 “max” settings. (default values in brackets)
max topics per day 
max private messages per day 
max likes per day 
max bookmarks per day 
max flags per day 
max edits per day 
max invites per day 
max topic invitations per day 
And there are Trust Level multipliers, but only for Likes per day.
tl2 additional likes per day multiplier [1.5]
tl3 additional likes per day multiplier 
tl4 additional likes per day multiplier 
My initial thought was to add multipliers for Flags as well.
Second thought was to have “universal” Trust Level multipliers that applied to all of the 8 max per day values.
That is, they would not apply to the rate limits (wait time) but only the max per day (but not the first day max limits)
True, the max flag per day setting can be upped, but as that applies to all members that introduces the (albeit rare) possibility of it being abused.