I think to have understood what you say. Your argumentation is valid, I think so really. But I, at the moment, remain in a lightly different position. And, not to confute your reasoning, but only to argue again and to make more clear my thought, I try to explain it.
I think that what really makes a contest more difficult than other one, it's not the number of participants in absolute (in some contests, the number of participants is enlarged by some occasional driver which would occupy the same positions in every contest), and it's not the quality of the tracks (I really think that the level is high everywhere). This is the reason to lead me to say that a race is equal to other one, independently in which contest it's competed.
If to win in some contests is more difficult than other ones, the reason is only that top drivers mostly race in several contests than in others one. And this happens, as I say before, for historicity or other factors, but not for the difficult of the race (as it could be for Tour, Giro or Vuelta respecting single race or tours composed by a small number of stages) and not for other particularities of the contest (as it could be for Wimbledon, Roland Garros, Open U.S. and Open Australia, where players have to win 3 set to get the match, condition which highlights the athletic preparation).
I absolutely don't want to subvert the criterias wherewith every single driver considers more prestigious a contest than other one. The "pioneer contests", which have brought Stunts on the WEB, sure have a particular fascination, and sure nothing and no one can take away it to them! And I really hope that the things remain exactly as they are!
Anyway, I think that it's not right to attribute more points to a victory in a single race of a specific contest, only because (for historicity or other factors) some occasional drivers mostly take part in it, or because (for the fascinating that some contests rightly have) an high number of top drivers takes part in it. And I think that there's not other technical factors (difficult of the tracks, lenght of the tracks or other ones) which can diversify the race of different contests so to justify a different scoring.
Finally, it's really difficult to choose or to establish which criteria should diversify the points to assign to a contest than to other one. I don't think, by aforesaid reasons, that the number of participants is the criteria. And I don't see, at the moment, other factors which could diversify the scoring of the contest in a rational way, not discriminatory or, anyway, arbitrary...
However, I will think about what you say and I try to refine current Stunts World Ranking criteria so to make it more precise and conformable to demands of Stunts World.