The part where you released two more climbers on the left, one to drop in the water, the other to dig, yours is a slight variation on how I did it. In my solution, I basically timed the second climber in such a way so that he still lands on a tiny bit of the stoner terrain that remains while the digger is still destroying it and hence falls safely to the steel platform below without splatting. However, the way the other one falls while over water is fine. I thought about blocking that, but not only will the level just be messy in appearance, it will also destroy the trick entirely, as then he'll just land on a steel platform higher than where he'll eventually land where the builder goes left over the gap, which doesn't quite produce the same effect IMO. Therefore, I'm just going to let it be and allow it. Besides, me being all nitpicky over just that? It's not worth it :laugh:
The main reasons why it's a very hard level: Digging down a stoner to make a drop safe, turning fallers in midair, and the extremely obscure trick of blocking and then stoning him to remove the blocker field to release the crowd, all tricks which are very obscure. The level goes even further than that: using a stacker to make a splatform, building a staircase and then digging a part of it away so that the climber does not doom himself to the flamethrower above, and finally bashing on steel to turn around. All of these in one level make for an extremely difficult level IMO.
Really besides enforcing the correct constructive skill usage on the left side, it was also very hard to force that the player must send the climber that hits the button in the upper left over to the top right side to prepare the platform for the swimmer to shimmy over. In all solutions before the intended one, you and Icho kept sending a non-climber and therefore there was no need to keep him safe when he turns back to the far right side after platforming and stop him from getting into danger. Also blocking the use of a builder to make a splatform was very hard. However, my fear of the builders being used to backroute the level were definitely founded here, as the player is given double the amount of platformers, 8 and 4, respectively. That right there told me in my mind, I have a feeling my R1, while being very hard, will also be the most troublesome to fix as a result due to how the builder is very powerful. In all honesty, I probably could had removed 1 builder and had the intended solution use a platformer in the top left/middle area instead and hence the level probably wouldn't be as backrouteable, but well, I just felt the building to be the better one for the overall effect/feel of the level :laugh:
Even then, the level is also very difficult due to how it's not very obvious whether to use a platformer or a builder for some of the gaps. It might seem that you can cheese the level by using two builders when just 1 platformer suffices to get over the gap (indeed, that's what happened a lot in the replays to earlier versions of the level from you and Icho), but then you'll likely not have the necessary constructive skill for a later part of the level. Thus, not being certain which constructive skill to use also makes the level hard.
Finally, perhaps the time limit isn't even needed anymore, but in earlier versions, it was definitely possible to maybe do the right side first and then cross over to the left to do the rest of the level without multitasking, and so to enforce the multitasking, that's why there's now a time limit. Otherwise, it's possible to just do one side at a time without sending multiple workers. Even then, I'll just keep it in for fear that the level will be majorly broken again without it, as the sense of urgency certainly "forces" a lot of the skill assignments in the level.