In the land of Sand, the big one has had FO's as trainers for years. Not so much now as the training has scaled back and probably only those that have medical issues now. Most have upgraded now.
On another note though is FO's in management.
We did have one guy who became 3IC on the fleet who failed his upgrade twice after three years in that position.
Don't think he's still here. However what a trail of disdain he left where ever he went. Not the most personable fella you have met either.
But l think the biggest issue against him was disciplinary hearings where he presided as judge/jury/executioner to, well, most guys senior to him.
The idea of his lack of experience in the hot seat riled so many.