Good, we have diverging opinions
That's good because we'll have to reflect carefully before reaching a consensus. Your posts did clear my ideas enough so I can now follow up with a longish post...
In a general sense, I feel any global ranking must average over some reasonable spectrum of required skills. Keeping up with BJ's tennis comparison, ATP rankings account for "all" top level tournaments, be them played on clay, hard or grass surfaces, and it is a fact tennis players are usually more effective at some surface of their preference. Maybe in our case the differences between, say, RH and NoRH are somewhat more pronounced (because they involve a whole change of "philosophy"), but I believe the argument still holds.
As for Indy vs. slow cars, most of the time it just evens up, since non-Indy-exclusive contests usually have a higher number of races with the slower cars than with IMSA/Indy. Any remaining bias can be pretty well managed by Mark's participation log-scale, which has as a vital characteristic not taxing too heavily top pipsqueaks with very good results but below-average participation rates. Proof of that is how Dottore managed to hold positions #3 / #4 on SWR during most of 2007 racing (and winning...) only at his favourite contest, USC. Even in a playing field with far more active (top) pipsqueaks than 2007 I do not believe he would drop from top 10 either.
Weighing competitions by their lengths seems to be a more delicate issue. Let's start pick the standard 30-day contest as reference. Should we raise Z84 importance due to the "bonus" 10 days? Surely not, as the impact on pipsqueaks' racing will be minimal, as Krys pointed out. On the other hand, giving the weekly races at JACStunts the same weight as a full month ZakStunts does not feel right, because this time is not only a question of different characteristics resulting in different advantages, for there are more quantifiable parameters involved. Should a set of four victories in JACStunts, each probably taking two or three focused attempts within a week, have four times (or three, or even two) the weight of a presumably long-fought 30-day ZakStunts victory? That would look like a strong distortion in favour of JACStunts occasioned exactly by the different character of each competition - exactly the situation we're trying to avoid.
Now, what about FTT and its novel (
) 3-week deadlines? Now we head into a sort of gray zone, as the subtracted week induces a change in racing style that is less about effort/time spent and more about different habits and tactics. For that reason, I believe while there's little escape of putting 25% weights on individual weekly races, FTT certainly shouldn't get a 75% weight - maybe 90%, or even 100% would be more appropriate. It seems the log-scale solution might also find some application on these issues, as additional or subtracted weeks are much more relevant to short-race contests than to long-race ones.
Summarizing, I believe it is possible to have a reasonably reliable ranking mixing very different sorts of competitions, even if we may have to wonder a lot over the fine details of the system, and that SWR success serves, at least partially, as an argument in favour of this theory.
Veterans, managers, newbies, keep voicing your opinions...