[oil pan 4]

AC gets better milage, we know. Its also 2 to 3 times the price and you cant get hardly anything off the shelf for building one.
How about this, if you make a one off AC drive system and some one puts it together for you what are you going to do when something breaks?

If you run DC then you have lots of options, get a bigger, better or up graded part when one fails. DC systems are easy to make scale able and are very forgiving, you can mix and match motors, controllers, battery configureations as long as you stay under the max input voltatage for the controler and dont over load the controler or motor.

If you have an AC system and one battery goes bad (say you are using 6 or 12 volt lead acids) I don't think you can just bypass the bad batt. With a DC system you bypass/remove the bad battery and keep going with slightly reduced voltage and preformance.
I dont think an AC system can do that.

I don't see why changing the brushes once every 6 months to 2 years is such a big deal.

If you want more power/range build a generator trailer or build a pickup so the generator can sit in back when you need it.
I bet you can rig up a DC set up with a generator and unlimited range cheaper than you can build an AC setup with regen braking.

Unless you are going to contract a motor builder and motor controler company for a minimum order to start producing vehicles then there is no reason for the hobbiest to try to build an AC system form the ground up.