Wow, this sounds excellent! Best of luck with this man...I'll be watching this intently. I have a React as well, and Cold Fusion (my dual BL Dagger) actually has a very similar setup with front and rear motors so this will be especially interesting for me. It's not setup as advanced as yours is going to be though, by the sounds of things.
By the way, just as an idea, maybe you could use a custom cutoff-voltage as a rudimentary current-limiter/traction control? When the cells are under load and the voltage dips, you could have a custom cutoff that activates when the cell voltage drops to a certain level. I don't know how the A123's behave though, so it might not work so well.
This should be awesome...have fun with it man.
