Unfortunately it's not really that easy to implement, basically because this means changing the code at a lot of different places:
- I have to add a new variable for lemmings, that store how many builders are queued
- I have to save this additional variable when saving the game state, so that they will still occur after backwards framesteps
- I have to change the replay code, because now it always saves a skill assignment when the lemming changes his work, not when the player clicked on it. This would mean that when loading a replay and modifying it, no skill queuing will ever happen.
So overall: A good suggestions, but not as simple to implement as one might think. I will certainly add this at some point, but don't expect it any time soon.