I tend to agree with Brent, and most of the other posters. It also seems that the .270 WSM, and .300 WSM
parent case make for a nice wildcat, I think that is the shortest case I would consider.
Most gunsmiths, at least from the posts I've been reading will use the WSM as the parent case to build from and use a long action magnum bolt face as the platform to build the custom rifle
from. Short actions tend to win in the accuracy department. Unless you are shooting bench rest I don't think it should matter much.
I think the long actions are here to stay. The WSM's aren't the best for the heavy bullets either, so the long actions will win out in that department as well.