The skills I had left over on Lemmerixo were 2 climbers, 1 builder, and 3 diggers. If the right solution "doesn't have more than two or three", that sounds like a back route, so here it is.........
Make the second lemming a blocker. The worker lemming mines off the top corner of the first platform then digs down the edge just far enough to build across the gap without hitting his head. Build up in a zigzag. Walk across the next platform, bashing through the obstacle. Dig down the edge again and build across the next gap. Climb up, mine and build to turn around, mine down to meet the bridge, and mine into the steel to stop the lemming climbing up. Release the other lemmings with a bomber.
The only difficulty in the entire solution is gauging the final miner, and even that is not very hard.