My second thought, that I haven't worked on yet but would be more suited for a location in filter.cpp, is to have some type of include directive in the filter file. I think I like this idea better as it allows for more flexibility. However, since # is used for comments I'm not sure the best way to denote the directive would be. One thought, which I think is a little ugly would be [include /pathto/somefilter.conf]. Similar to the first idea, would have to split out the actual reading/parsing of the filter file to a new method so the includes don't get wiped out by the clear, but overall I think a better solution to the whole problem.
I would like some input on the two ideas and I will work on putting it together and getting a patch for it. Of particular interest to me would be comments on the second solution and how to denote the include directive since that is the course I would rather take. The only other thing that would be missing is to know LOGDIR inside of filter.cpp. How much havoc would it cause to #include "main.h" in filter.cpp?