The ACP system is the benchmark standard, no one can touch it (yet). They use the armature/windings of the motor as part of the charging circuit, they support about an 18KW max charger, with no additional weight for the "Charger".
Its very expensive though, pricing out at over $30K for the drve unit/electronics, so perhaps Tesla could have used it, even then its too pricey, for a $57.5K car, as the batteries are the largest cost, then their is the dirve train, chassis, etc.
It would be nice if ACP "saw the light" and licensed its technology for a much more reasonable price, perhaps in volume, the costs could be lowered to a reasonable level, and they could get a license fee, or a per unit license fee. Sadly, I don't think thats ever going to happen. They are also leaders in V2G (Vehicle to Grid).
They have a technology too expensive to deploy, that no one seems to be able to afford, so they've solved many problems with an inovative design, but its not price competetive.
Reductive Drive unit/charger: http://www.acpropulsion.com/products-drivesystem.html