10 amp-hours is too small for the LEAF's idle-power requirements if the vehicle is parked for any appreciable length of time. People come home to dead batteries after less than 2 weeks vacation, and that's with over 40 amp-hours of capacity. If the battery's internal cut-off voltage is high enough, it might work. It might be convenient for people who do use long-term parking, giving automatic cutoff. But could be a hassle If it cuts off over the span of a long weekend when you're not expecting it, disabling telematics, timers, etc...
The LEAF has no need for a capacitor bank providing "starter current" so that's a lot of wasted technology.
Might be useful in some special cases but not for most drivers, imo.