Boss Hogg, all those wildcats will work with the magnum bolt face. That was how they were designed. I would hold off on any WSSM stuff as the rumor mill has it that the WSSM is heading for the cemetary.
Of the final two you mention, I would go with the 35-300WM. The 30-338 is way too close to the 300WM to worry about the huge costs.
Will it do anything differently from the 30 or 338 on large grass eaters? Probably not but that is most certainly not the point.
As Guntech said, the 340Wby is now common fare but work it most certainly does. 225 to 250gr bullets put a big hurt at both ends.
On that note, there would be the 338STW, 35STW, 375STW, 404STW, 410SomethingorOther, 45Lott....
Jerry