Hey,
I know with UE4 the options for AA are limited due to the deffered rendering path. Have you guys looked at TAA?
I know it can give a slightly blurry image, however there was an UE4 document released which perhaps the devs could look at which may help with that?
https://forums.unrealengine.com/development-discussion/rendering/1449167-sharper-image-without-the-edge-artifacts
Thanks for reading.
Ben.