I agree with most everything you say, Howard... except that the 50mm Nikkors are not renowned for being the fastest-focusing lenses out there. By AF-S standards, the current AF-S 50mm f/1.4G is not a speed merchant and is said to be a little slower to acquire focus than the previous AF-D model.
And - you don't have to use a zoom like a zoom - if you see what I mean! It's quite feasible in the sort of circumstances described to pick an approximately-suitable focal length and leave it there. Used in that fashion, I don't think the 24-120mm would be much slower to acquire and track focus than the fast 50's unless light levels are really poor.