Composite by cameras.

How could I set up a scene so that each camera in the scene has different compositing effects tied to it (blur, DOF, glare, etc.) so that as the active camera is changed, the effect changes?

The easiest way is to make seperate render production files on camera changes.
Use compo setup A for active camera X from frame 1-100, save it.
Delete setup A and:
Use compo setup B for active camera Y from frame 101-151, save it.

Feed the frames in a renderfarm/renderqueue.

Or use duplicated scenes with a different node setup on each, then call each scene into a seperate strip in the VSE.

Thanks. I took your advice and it worked.