I think for Fun 23/Taxing 17 it should be necessary to specify whether you took the visible exits on the left or the hidden exit on the right. Based on my playing of the Fun version, I'm guessing you guys took the visible exits route. However, I was able to use 1 less builder. Same number of bashers, but 1 less builder. Shortly after that, I was able to reduce the number of builders, as well as use 1 less basher and hence bring down the total number of skills down to 18. 11 builders, 7 bashers. So, 5 less builders, 1 less basher, and so 6 less skills overall. See my replay.
Takes advantage of the fact that I bashed to the right with the lemming and canceled him midstroke with a builder so that one lemming turns back way before the others while the rest can still continue to the right, and I also bashed away the staircase so that when the lemming builds to seal the gap back to the left he doesn't hit his head very early. Now it might be possible to just use one builder had I positioned the builders better, but I still had to use a second builder to seal the gap completely.
After that, I decided to try for the hidden exit on the right. Here, I got 14 builders, 9 bashers, and so 23 skills total. See my replay. So even though I bested the record in the OP by 1 less total skill, here I reduced the number of builders by 2 (-2), but I used 1 more basher (+1), hence -1 (-2 + 1 = -1) net effect to the total number of skills used. So, it seems that it'll always require way more skills than the left visible exits, especially since I don't think it's possible to get anywhere near the 18 skills total I used for the left exits. So, perhaps it's not necessary to specify which exit you went for in the level, although I still think it's a good idea to and try and improve results just for the exits you went for, like how I drastically improved the result for the left exit with just 18 skills total. Now, can anyone improve my 23 skills total result for the right hidden exit?