Some users want to have a single line audit log formatter. I think it would be better to have the ability to add your own formatter from a module, something along the lines of:

<custom-formatter code="org.blah.MyCustomFormatter" module="org.blah/mymodule">
   <property name="layout">...</property>
   <property name="propB">...</property>
</custom-formatter>

We'd need an SPI, and a slight reworking of the audit log internals. In any case doing this will put us in a better position to provide the single line logger if this proposal is not acceptable to our users.