The Leaf has optional battery heaters for use in cold climates.I'm amazed that the Leaf does not have an active thermal management system.
I doubt this would help very much because each battery module has a lot of thermal mass and I don't see anyway of removing the heat easily.I've been considering fixing some heat-sinks onto the additional battery packs I will add to have the wind under the vehicle help to pull away heat from the batteries.
It's difficult to quantify the impact although I guess if you're drawing half the current then we would expect a reduction in heat build up.Is it reasonable to assume that if I double or triple-up the battery from the original Leaf, that the strain (and heat) on the original battery would be lessened?
Note that the latest 40kW Leafs overheat much more readily than the 24kW/30kW Leafs. You may want to factor that into your battery choice if you're convinced you have a problem with heat.