[BrianG]

1) Those voltage controllers are simply voltage boosters to get higher voltage to your ESC. However, this added power is not free. These devices will pull more current from the cells to do so. Think of them at "power transfer devices". Plus, they have losses. It would be better to add an extra cell IMO. Why not pick up a Dewalt pack and make your own setup? They come as 10s, but you can set it up for 5s2p, which would be perfect for you.

2) You could, but the current will be quite high (runtime low). Either your motor will have to have a higher kv, or your gearing will have to be higher. Either case will pull more current. I'd stick with at least 5s2p A123s.

3) For the price of the charger, I would simply find a different charger that will do more. If you are into Lithium Ion/poly, then the Xtrema charger is quite nice. I like mine (does 10s at 8A with a 180w power limit and has programmable CC/CV threshold settings from 3.6 up to 4.2 in 0.05v increments).

4) You can charge up to whatever "s" count it is rated for. If you charge the packs in parallel (I would not recommend this), you could do it, but it would take longer.

5) Don't know about the ICE.

6) Zeropointbug seems to love these cells (almost too much if you get my meaning ;) (j/k ZPB)). If you want Lithium-based cells with safety and durability at the expense of weight, then these are the cells to use. If you want minimum weight at the expense of durability and safety, then Lipos are your best bet.