Buying a front brushless hub won't solve your problem - you need a better or larger battery. Talk to ping (ebay ping227) and he could set you up with 24v 20-30ah battery.

Even with larger capacity, it will be about same or less weight than 2 of your Currie batteries. And the cost should be about same of buying a front brushless kit - $400 range (lower end). With very mild pedaling, I used to go 40 miles+ on 20ah battery.