What you did at the start was a bit unintended, but I'll accept it, especially as everything else after that was the intended solution.  The intention at the start was that the first lemming starts building a few steps ahead of the trapdoor, the second lemming goes past, the third lemming becomes a "pass-through" blocker right below the trapdoor, and then the builder becomes a blocker before the fourth lemming passes.  You then release the first blocker with a miner in the crowd, and the pass-through blocker is released by the climber mining underneath, who can then escape that small alvove by climbing out.  I may still patch it, but it's such a minor thing and you would easily be able to re-solve it even if i didn't tell you the solution.

It was intended to give 2 Bombers on Cunning 16, both to look symmetric in the tools you are given and also to see if you, the player, are paying attention!  An earlier level in Curious has 20 Bombers, but you have to save 100%... a classic Mayhem trick!