Here is a trick!

I think I used this once or twice.

Instead of trying to manipulate the pivot points axis';
1) Make a primitive
2) Rotate the primitive to align it to the objects you are about to scale bigger
3) Parent the whole thing to the, say a cube.
4) Adjust the cubes pivot point if needed, to make your bunch of objects scale bigger or smaller from a certain centerpoint.
5) Then scale the children by scaling the parent cube.

I'm sure this works. Your objects will inherit the scale-axis' of the cube.