I thought that Speed was overpowered once too. So I tried making a warrior with 10 Speed, 5 everything else. It was not the fearsome monster I thought it might be. Instead, he whiffed tons of attacks, even on the low level enemies he was facing. Getting an extra attack per round was not terribly helpful, since I missed most attacks anyway.
Having only 5 Constitution is also probably not a good idea for a front-line warrior, since the warrior is already a bit too squishy as is.
You are correct in that warriors tend to be slow. I'm not sure that separating movement out of action points will be very easy to do, and I'm not sure doing that would make it any easier to balance warriors and ranged characters.
