Actually I have found Champaign yeast guts the beer, used just as you describe, I would avoid it.
Been thinking about the available nitrogen, there should be enough available in a wort (not in a mead or cider/perry - for sure)
I doubt it would be necessary to go to the trouble of incremental nutrient additions, a good dose at the start wouldn't hurt. As much for all the trace elements (especially Zinc) that a good nutrient contains. The yeast should be able to assimilate what it need from the dissolved protein.
Don't know for sure, would have to do some experiments, never taken a beer over ~17%, it was a bit fusely and took a couple of years to develop reasonably, its hard country to brew well in, high ABV beers are a challenge.
We knocked out a 12% barley wine with the HA18, surprisingly quick (90 points in 8 days), likes to run warm, and finished much lower than I expected, it's just gone into keg and off to the cool-room for a long slow secondary and maturation.
Tasted very good out of the fermenter, still plenty of body despite the low FG. I suspect it will get a bit of Oak at some point.
Mark