There must be a reason that you haven't bought the existing HV car controllers already, right?
See sig below lol
The data I posted is from my ET testing on my Revo. I'm not making figures up. My only complaint of the MGMs is the reverse issue, but that's w/ all. If they tweak the software its a 100% controller. Otello is running a Jazz 55 on 10S A123 and its very smooth also.
I almost forgot. I also ran my Kontronik 3SL 40-14-32 with 2 36V A123 packs in parallel in my BPP truggy. It ran awesome and being an old ESC it only blew the small capacitor. I will fix that controller and maybe add some more caps and a heat sink (Not really needed).