$15 / $1.75 = 8.57 cells per $15.
Amps = 1000 watthours / (3.7 volts x 8.57 )
= 31.5 amps per cell.
Panasonic Battery - Panasonic NCR18650PF 2900mAh 10A Battery
www.imrbatteries.com
"Discharge Current: 10A Maximum Continuous"
You're going to get 31.5 amps out of 10 amp batteries?
And, do you really care about power out of a battery?
You've already got 2000 of these you say... that's already 2000 * 10a * 3.7v = 74kW, or 100hp. Or, supposedly, 31.5 amps or 300+ hp short term.
And you're planning on having a lot more than 2000 I presume?
Power isn't really your limitation, energy will be.
So... what happens when PVC tubes, in a vibration-heavy environment, through sharp bends, in heat and cold... break?
You're going to hose your batteries with water and antifreeze?
I like your solution but, I'd worry about imitating it. I am also doing 18650s, but I have no cooling solution other than perhaps forced air and a prayer (my are square packed, which does leave a fair amount of airspace for cooling).