Could the units CURRENT training, have a modified (diminishing returns style?) effect? Where Very High and High Training decreases more rapidly, but lower training (say under 50) slows down and takes a much greater and prolonged time? With the idea being that once under 50% training, there's not a lot to lose, and once you hit like 35-40% . . .well, even the most fresh recruits can do that, so they can't really drop too much lower (and if they did, it wouldn't be too noticiable).
I don't know what the current mechanic is (I've never bothered to look), but this sounds like a reasonable proposal. Knock down the elite status pretty quick without constant attention, but it's hard to lose much when you don't know much to begin with.
