The main reason we don't currently produce a 14 Ah plus battery is cost-the 10Ah battery seems to have become the standard in China,is produced in large numbers and is good value-the bigger capacity batteries are a non standard purchase and therefore subject to pro rata additional costs. But the LifePo4 battery is becoming the prefered choice of replacement to Lead Acid so that situation may change in the near future-I will e-mail my battery manufacturer to see what the current situation is.
Dave
KudosCycles