RE: Chademo rapid charging
What the battery is capable of is only a slight comfort. The socket could be changed relatively easily, but the wiring loom? That would be a major issue, and that's before you ever get to the replacement chager electronics. Yes, the Zoe Chamelion charger might be a candidate, but will it fit? You then have to upgrade the cars firmware and from memory this is locked down.
In the UK you would have to seek approval from your insurer before they provide cover on public roads and many are not fans of modifications of any sort, never mind homebrew ones. Then there's Renault.... your 4+ warranty is invalidated, as is your battery lease (have you read it?)
And even if the car DID work after all this, for what ultimate benefit? Charging a bit faster? I'd never recommend or contemplate such action as what do you do after you've bricked the car...? Sell the remaining cells to Leaf owners to experiment with, and wave goodbye to the rest as it goes to the scrap yard?
That would be vandalism in my book!