Using a voltage regulator is a first for me, but it seems like a bad idea for a few reason, not least because even brushed motors can pull peak currents way in excess of 100amps under the right (or wrong...) circumstances- that would blow the regulators to bits. Best option would indeed be lipos; for as much as I love the A123s, they are a pain sometimes due to size/weight/ funky voltage. Zippies are best value for money by far, even if the QC isnt as good as it should be (thats what the lincpimp is for
)- havent looked at kershaws lipos, so cant comment (if it says maxamps on the label avoid it like the plague though). SPC and trueRc lipos are very good too, as are Mike's own brand items in the rc-monster store- depends how much you want to spend really (I have a list on my website of good places-
http://robotwars.00server.com and its on the truckslinks page if you scroll down to the battery section).
Your list of hop-ups looks pretty good- probably better to go with BL really, even if its a milder hvmaxx system- replacing brushed motors every 30-50 runs gets rather old rather quickly, even with the beefier Kershaw drill motors.