I'm almost certain this can be done on Taxing 30 and Mayhem 11 as well.
My Fun 10 challenge has turned out to be quite difficult (as I expected), so I will offer an easier version:
As before, but you can use builders as long as:
- you destroy any terrain you add to the level with builders, and
- you don't start a builder from anywhere except for the central block of terrain or another builder bridge.