Elemental Affinities in Indomitable

Since I've gotten a few questions about it I thought it might be worthwhile to take a moment to explain the interpretation of chakra natures that I'm using in this story (and probably in FWoaJ as well, if it ever comes up there).

Unfortunately this is one of those areas where the source material isn't very clear, as Kishimoto apparently isn't the kind of author who writes up his world's background in any detail before starting the story. It's pretty clear that the whole concept was invented after the end of the first series, and in the canon storyline it serves mostly as an excuse for training scenes and a reason for everyone to be impressed when someone like Kakusu throws around jutsu from several different elements. But anyone who wants to really explore potential power-ups in the Narutoverse is going to end up needed a more detailed concept of how elemental manipulation works than the vague explanation Kakashi gave Naruto.

The interpretation I'm using is that anyone can gain the ability to use any element by going through the appropriate training, but most people can only reach a useful level of ability with the element(s) they have an affinity for. With any other element your conversion of normal chakra to elemental chakra is such a slow, inefficient process that it's useless in a fight. Some ninja will train multiple elements anyway, which lets them use piddling little utility techniques for elements they don't have an affinity with. Every now and then one of these people finds a loophole that lets them gain additional affinities, or switch affinities, or one of the other related tricks we've seen people like Fuka and Kakuzu use.

In Indomitable one of the ploys Naruto tried during the time skip was having clones do the basic training on all five elements, in hopes that his massive chakra level would make the normal limitations on using foreign elements moot. After all, he can afford to burn ten times more chakra than normal on a Grand Fireball if it's going to get the job done better than a Wind Bullet. Unfortunately he discovered that he still can't convert normal chakra to elemental chakra very quickly if its a foreign element. Combined that with the increased chakra cost, and he'd end up taking half an hour to gather enough elemental chakra to throw something like a Water Dragon. So he hasn't bothered to learn any of those high-level techniques, and he tells Anko that he can't do them (meaning, 'can't use that kind of thing effectively', not 'couldn't possibly pull one off under any circumstances').