But this system is different in that it increases both the total HP and torque available (unlike the Ram eTorque system).Most of these trucks have plenty of power for towing, the hybrid supplements to reduce engine demand and reduce fuel consumption. Given the hybrid power will not always be available, and certainly not for long duration situations, I can't see it as increasing actual tow capacity.
I get though a bit of what you're saying when you say the F-150 engines already have plenty of power. I went with the 4 cyl. Subaru rather than the 6 because I felt that was adequate. People tend to get more powerful vehicles than what they need because that's what the car magazines tell them they need. But for this truck and towing use I was thinking not only of power driving, but also power camping. I've not done the math, but I suspect the 1.5 KW battery would only give you maybe an extra day of 12 volt power if you weren't using much power camping. So both the extra power towing and camping would be nice, but neither is earthshattering.