Apache Maven created a Groovy monkey patch to extract such renderThrowable() and renderLevel() and being able to override these methods in a local provider, which is essentially slf4j-simple with a little rendering improvement

see https://git-wip-us.apache.org/repos/asf/maven/?p=maven.git;a=blob;f=maven-slf4j-provider/src/main/script/patch-slf4j-simple.groovy;h=bba864662f70a2ed06aa9a4c5da50df895d7bbed;hb=HEAD

Having these changes directly in slf4j simple provider should not change much things, and would avoid us the Groovy patch dependency: the provider will still be required, since we can't have 2 providers in the classpath, and adding real extension/configuration to slf4j simple is much more complex