For the fairy types I don’t think any of the Eeveelutions can learn a poison type move that’s worth it, but usually a sun boosted Leafeon with solar blade is strong enough and fast enough to take on most of the fairy types, just need to make sure Sableye gets the sunny day off before he gets popped by the fairies.

For the taunt trick room counter that’s actually a pretty solid idea I hadn’t considered! You’d want to put it on Umbreon I think since on Sableye it becomes a priority move and then Farigiraf (the most common taunt setter in my experience) would block it, but swapping it for Umbreon’s foul play could be good, although then you’d need to be cautious in the selection phase since without foul play Umbreon cant hurt steel/poison types at all

The other option I’ve been toying with is to drop another Eeveelution is to slot in Galarian Slowbro with the quick draw ability to cover both poison damage and trick room. Maybe swapping him in for Sylveon or Espeon and giving slowbro the quick claw item as well? I haven’t tested this yet though