In my opinion, and this is strictly because of how I view the utility and future of EVs, you are not really doing a service to your customers by JUST extending the autonomy of a car without also significantly improving its charging characteristics. Especially on the leaf with its legacy CHAdeMO connection, IMO you're skating on thin ice by providing another non-thermally managed pack. Moreover, because developing and supporting an EV battery replacement is a very long-term commitment (it takes ~2 years from start to finish to develop the thing, then at least a year to turn a profit and at least the lifespan of the battery - say 8 years - of support even if you stop production after that year), it's important to consider not just the needs of customers now, but those of customers - essentially - 8 years from now.
In 8 years, those LEAFs will still function just fine mechanically, I have no doubt about that. But nobody is going to use a car with 50kW (really more like 44, and only peak) fast charging for anything beyond a grocery runabout car. That's honestly not functionally different from an unmodified car, so why even bother with the extra range. From a sustainability and GHG abatement perspective, you've not really improved the world at that point. People still need a second car to do serious car things like drive 200 miles - especially in car-dependent places. I want people to avoid needing another car with all the emissions and traffic implications that may have.
Now, thermal management is not just battery cooling, it's also heating. And that's really where the LFPs are horrible and should be thermally managed. They suffer massively from lithium plating at even moderately low temperatures (e.g. 0-10C), so you get maybe 0.25C allowable charge rates (~10kW) at 0C and 0.5C at 10C (~20kW). Considering that the car also has higher consumption at low temperatures, this makes the car nigh unusable for anything beyond its initial autonomy, and even threatens slow charging speeds at freezing temperatures.
So for both usability and technical reasons, I expect an LFP pack to be fully thermally managed.
In the future, I basically expect three tiers of battery replacements to be competing for people's dollars:
- Salvage packs, cheap and shitty, sold at like $50-100/kWh
- Salvage-like new packs, with similar capacity to old Leaf packs, maybe even recycling their shells to keep costs down, with no thermal management, sold at about the current level of salvage packs ~ $150-200/kWh
- Re-engineered packs with higher capacity, much faster charging, thermal management, coupled with e.g. CCS retrofits, sold at $250+/kWh
And both from a business and user's perspective, I expect only that last one to be acceptable, with the others mostly being a cheap fix for actually broken batteries to tide somebody over for a year until they buy a new car.