Tightening up the map is the wrong idea. You're just constraining the little gameplay it has and making it easier for snipers to make kills. Those teleporter exits are out in the middle of nowhere and you're better off walking from the base--they do little to balance the vehicle path with the foot path, especially when you teleport to an area with only narrow one way out. I think we've had enough of the canyon maps in Halo. Think of something that's never been tried before. It's fairly easy to draw some squiggly lines for cliffs and call it a map, but what I sometimes do for inspiration is find a neat looking object in my house and imagine how its surfaces could be turned into a map. You can always use Google to find interesting terrain as well. In addition, your spawn area looks too big compared to your bases. It's best to spawn players at their base where the weapons, flag, and teleporter are.