I would like to back up a bit.
What would be the effect of a FAC assuming the can/no can issue were not an issue. To the best of my understanding it would even out the differential between the fast and slow divergence and the beam that passes out of the collimator would be more symmetrical ie. circular, but the product of the beam diameter and divergence would be roughly unchanged. If that is correct, then we are accomplishing this now with our macroscopic beam correction optics which must be cylindrical because of the dis-symmetry.