Actually the small, slightly larger than human mechs are very much a possibility. Giving the mech a standing crew compartment, with the legs running into the legs of the mech and arms in the arms, the mech could be armored with the new plastic armors being developed which are highly effective and VERY light. They could be incredibly mobile, and run off a variety of power sources. The sources could range from gas turbine to electric motors. Mobility would be amazing allowing the mech to go prone, duck and what not. The mechs could be very cheap in both man power and construction and could help provide protections against the new bio and chemical threats on the battle fields. As for offensive power, the vehicles could have built in machine guns and light cannons for soft targets or even mount hellfires for Anti-armor.