I think the main issue is predictability of price/power? If you could guarantee getting paid 10p unit for off-peak, and guarantee getting paid 40p to supply during peak, for say 5 years, I think a lot more of these projects would take off...but it's all still far too turbulent.
The thing is: batteries, when used for buying low and selling high only in a turbulent market, have a dampening effect on exactly that. So, if deployed en-masse, they kill their own business case. With the 'side effect' of a much more stable price market, which is exactly what we want I guess.
