I would also keep dragoons in addition to the ones Slashley mentioned. They are very niche as well, but comes in handy occasionally if you don't have kaisers.
Radon also has a really rare active - reduces rage bar by 15% iirc, more than Archangel which is 10% iirc. Theoretically can be useful but I wouldn't normally use it unless there's coordination with other players.
As mentioned, UEs will come back. There's also going to be a new shop next April-ish that sells HSP.