The boilerplate is also tricky to generate.
Some code interpolates strings (which makes it difficult to defer naming decisions).
Other places generate minifiable boilerplate via hard to read code that constructs sequences of statements etc.

My rough idea for this is:

1. Expand parsing JS code to include statements.
2. Do #-stubstitution in two phases: (a) parse to a template (b) apply template (mostly a tree clone).
3. Add a named version of #, since positional will get tedious with larger texts.
4. Convert all (or most) JS construction to use templates.
5. Allow # in more places to implement property, identifier, string and list interpolation.
6. Remove legacy API to ensure JS ASTs are immutable and share structure where possible.