Ok, I revised the pack to remove some backroutes. I hope. At least, re-try 5, 6, and 7 if you didn't find the "real" routes in the past.
Also here's a text file with hints and solutions.
Steel digging is still possible in level 9, allowing you to waste a builder somewhere in the solution.
Pretty certain I found the intended solutions for 5 & 7 now; retrying level 5 I suddenly realized you could easily send an athlete down to the bottom, something I had previously overlooked. With that in mind, I found the solution pretty quickly and didn't look out for more complex routes.
In level 6 for a long time I blatantly overlooked to most efficient way to do the ending part near the left exit (as you'll remember from my previous replay), but now found a solution that looks to me like it might very likely be the intended solution, the only issue is that there's a leftover builder. Using this additional builder, another route is possible which does not use the key element.
I like the idea a lot, especially having 7 floaters which seem like they'd go to the right exit, 7 climber for the left exit and one leftover lemming; the actual solution still making use of these number, however in a different way.
Solutions via e-mail in a few minutes.