It appears I've reinvented a worse version of your wheel. ^_^

Your ssexpand-all is superior and I'm using it now. I did try to refactor it, thinking there must be a function f (like my ssexpandif but more sophisticated) that satisfies

(treewise cons f expr)

while producing the same functionality, but I haven't been able to determine what that would be.

arc> (ssexpand 'a:.b)
(compose a .b)
arc> (ssexpand '.b)
(get b)

So, we need to recurse in the f argument anyway. At a certain point, it seems like the anonymous & higher-order functions add layers of indirection on what should just be a straightforward recursive definition.

I get really annoyed at that, though, when working with trees in Arc. There always seems to be some underlying pattern that's just different enough that I can't abstract it into a higher-order function.