There is no "vanillla TS" ladder and mod ladder. They are one in the same.
I have been thinking about if the maps on the 2v2 ladder should be rejectable but the thing is, as long as the maps aren't insanely skewed to favor one faction, there should be no valid reason to allow rejections. The point of the ladder is to showcase skill as well as to reward effort for people who decide to grind it a lot. Letting people cherry-pick the maps they want to play completely voids the entire reason to even have a ladder in the first place. There is a reason I am being highly selective for the maps that will be added to the 2v2 clan ladder since the 1v1 ladder was a HUGE bungle... To be blunt, giants shouldn't even be allowed on the 2v2 ladder due to the severe favor nod has on it, but I am letting it be there because I don't want to alienate modders from the ladder.
If I were to allow rejections, it would be another separation of modders and ww players on the ladder because modders would reject westwood maps and westwood players would reject mods, which also defeats the purpose of a rank. As long as everyone is willing to play any map, there should be no issues with competing.