Well, if you don't mind doing all the tedious connections yourself, I don't see why not-just remember to use several parallel strings of series, otherwise you'll end up with a very high Voltage pack of 2.7 Amps.
And Bennelson-if you're going to Turbocharge a PWM controller with a Contactor(and risk the sudden jolts damaging it) why not just use a Contactor Controller with Amp Limiters on the Batteries and freewheeling diodes on the circuits to prevent Contactor wear? The old Analogue Controllers probably won't care about the sudden additional power, and the diodes should reduce Contactor wear, with the Amp Limiters just helping your EV FE a bit...
http://www.diyelectriccar.com/forums...ion-27537.html
There's an interesting idea being discussed here, of Volt-controlling the battery output with a software-driven Auto-switcher...it logs in one battery at a time as needed, and in order of the strongest battery currently in the string. If this method is perfected, it would make a cheap and effective alternative to PWM, I think.
Mind you, I don't see how the Switcher or the Contactor methods would work with NiMH or Lithium single packs-you'd probably have to keep them separated into discrete packs and separate chargers or something...