Very good write-up, thank you. I'll tell you straight up that the ONLY thing that totally turns me off hybrids is the battery - because here in NZ, no-one buys cars new, and we often buy cars that are around 8 years old (ex-company cars, ex-Japan used imports) - about the end of the warranty period for a battery pack. A Mk 1 Prius battery had to be replaced at a cost of NZ$6K (about GBP3K), and when most people spend (or more correctly, finance) that 8-10 year old car for $8-12K, the battery pack defeats the purpose in getting the car.
It's good to know, as you said, that not all of the modules need replacing, in the case of the Leaf anyhow. That makes it more viable for many people. According to US Consumer Reports, the battery pack degrades to 80% by the time the car is 5 years old. I'm just wondering if many of the modules degrade at a similar rate, in which case you'd end up changing more than a few of them within a short period of time.
Small world - I'm originally from N.Z. myself. I too am more interested buying cars at the age when they've done the majority of their depreciating but are still good. I guess when buying an eight year old Leaf, we'd need to find one that has had its battery replaced. From what I've read more recently, Nissan currently want to replace your battery for $5000 U.S. And give you $1000 rebate for your old battery ($4600 NZD in total). But that's not to say in 2019 they'll have the same guidelines. As time goes on, batteries will get cheaper and maintenance will cost less. It's in Nissan's best interests to make batteries as cheap as possible, because their current massive expense has certainly deterred many potential buyers. So they may well start replacing bad cells rather than entire battery units.
The future is not having to charge EVs at all. We'll simply roll into a charging station, your flat battery will get automatically swapped with a new one in seconds and simultaneously your account will have funds deducted. The charging stations will own all the batteries (like gas cylinders in current service stations).