Alain:
I like your brainstorming because you just might come up with an idea or two that I haven't thought of before... so don't let me slow you down too much....
However, do note that there are some limitations to the "if on more than one list, probably not an FP" philosophy.
This philosophy works great if the potential FP was due to "stupid human error" from one guy regarding one list. However, there are a number of scenarios where a mass mailing spam campaign may trigger a URI to get listed on multiple SURBL lists, even if that particular URI is found in ham. Of course, we do all that we can to minimize this possibility... and I believe that we are doing a great job and we are continually getting better...
But, again, there are diminishing returns to the "if found in multiple SURBL lists, less change of FP" idea. This is true to an extent, but **not** always true.
Rob McEwen