Here's what I've been thinking...with much of Europe and Asia going to 5 cell in TC the A123 packs are closest to 5 cell. I think this is why Tamiya decided on that route instead of LiPo. If the US goes to 5 cell in TC as well then the A123 would be a good fit there and since it can fit into 1/12th it might be a better option for 1/12th as new drivers who want to race 1/12th would already have all the equipment including batteries. The downside of the extra voltage might be off-set by having 21.5 as the stock and 17.5 be the super stock.
Then again if the US doesn't eventually go to 5 cell then we are still stuck with the same argument we have now.