Changing the default warning threshold is easy, it's just a #define.
Although setting it too low would spam syslogs on some setups.
When I was trying to cram stuff into 4k in the past, I had a patch which
added a sysctl to dynamically change the warning threshold, and
optionally BUG() when I hit it for crash analysis. It was good for
debugging, at least. If something along those lines is desired, I could