This doesn't exactly answer your question because 1) I didn't take HIGH dose vitamin A and 2) I really can't speak to how risky it is. (Though I wouldn't do it myself, personally. I just feel like mega-dosing always comes with a downside.)
That said, I did see a dramatic improvement in the clarity and texture of my skin since taking a dose of fermented cod liver oil/butter oil blend. Nothing huge, just 1/2 tsp a day. My acne wasn't extreme (though it was pretty bad when I was younger), but I had breakouts, lots of redness, and a rough texture that never seemed to go away now matter how much (or how little) I exfoliated. It took about a month to see a difference, but when I did it was remarkable and it hasn't gone away, even when I have stopped the FCLO/BO for weeks at a time because I ran out or something.
I have seen similar improvements with topical retinols, but those have always had a strange hook effect with me--they will help for awhile (a month or two) and then my skin seems to adapt to them and go back to its original state. I have not yet experienced this with the FCLO/BO and it has been about 6-7 months.