geeberry can give you terraformer perms. I'd recommend just individually forming the levels of the hill using a cyl/disc brush ("/br cyl <block> <size> 1" with WE, or "/ts b d cc" with terrasniper), it's totally feasible for a relatively small hill and will likely give better results than the erosion brushes anyways. The only limitation currently for doing hills is the lack of the powersmooth script, everything else should still be the same as before.
Gmask doesn't work with //smooth, or at all?