If nothing else works it should be possible to control the chance of spawn by duplicating the exact same entry in a ratio with the others in the group (5x Vigero entries, 1xDukes entry. Vigero 5:1 Dukes spawn ratio etc).
Just in case you don't know (or for others reading this), you can do that in 'dispatch.meta' as well, to influence the likelyhood of a certain dispatch vehicle spawning in relation to others in the same ConditionalVehicleSets VehicleModels section.
never followed this route, but I guess something along these lines
mods\update\update.rpf overrides all x64 archives and dlcpacks so if you want your custom carvariations.meta on vanilla models then eg add a carvariationsmine.meta inside update.rpf, refer to it in content.xml and this way it'll override the color sections for listed models in other archives?
Ok so for the Contender SWB REPLACE mod I used the original Contender META files from the Cunning Stunts RPF. It crashes right? So I guess one thing I never tried was to just simply use META files from the base game RPF.
What is the Contender more close to do you think? Sadler or Bison? I think I might use one of their META files and see what happens...