Personally I think if they do start adding in 4-man hard dungeons/raids, they should make Castrum and Prae the first ones. Have Livia, Nero, and Gaius armors be rewards for it, both the White Devil and Red Baron mounts be VERY RARE drops, meaning you can still get it or just buy it now and not have to deal with RNG.

Also a little Ultima Weapon minion, for funs.