Vehicles are nice but the map really has to be built for them, and there has to be accessible weapons that can counter the vehicles. Maps with jets have to be large, maps with land vehicles need to have wide open corridors that vehicles can get through easily
That being said if you add vehicles, don't force the players to rely on them, since they are so unreliable. Nobody wants to walk to an outpost for 5 billion years because 3 people on their team are currently driving the only 3 available 50-seat APCs, and then get shot dead and have to do it again. Build your map as if everyone playing it is running it on a stuff computer and has the view distance all the way down