I thought of something similar to your surfacer a while ago. Tying it to a climber however seems to be somewhat limited to me (like the runner usually only being useful in combination with the jumper). That's why I suggested to make a version of the L2 Twister which goes straight up. It would either require to make a terrain check at the Lemming's head rather than its feet, or to jump up a certain height, like it's being discussed for the Shimmier. More importantly, once the Lemming is finished performing the skill, it would have to move a couple of pixels in the direction it is facing, to prevent it from falling straight down again. Similarly to the digger, the Lemming would be in the centre of the shaft it is creating. It also couldn't be allowed to check for terrain beneath its feet during skill performance, like with the builder.
Speaking of building, about the downward thing: Wouldn't that be a case for the L2 Roper? Obviously, it can create upward and downward slopes, as well as horizontal plains, so it can easily break levels if the creator is not careful. However, I found the limitation of the distance the hook of the rope can travel, as well as the maximum angles of the rope, to make the skill a fair one overall. From all projectile-based skills, I consider this the most useful one, a lot more versatile than the thrower, bazooka and other projectile-skills which have already been promoted.