Even if we forgo line directives, there's the separate but related issue
of permitting an arbitrary datum after #! directive.

Scheme currently only uses identifiers: e.g. #!r6rs, #!fold-case.

Instead of identifiers, we could permit arbitrary datums: #!(foo bar
("baz" 123))

This would let us type stuff like:

#!(file-info (author "foo") (requires ...))

This proposal is also bound to be controversial in whether we should
have it at all. But it's semantically easier to deal with since the new
syntax is unambiguously Scheme syntax, not external syntax embedded in a
Scheme file.

If people want this, and don't want to parse line directives as Scheme
datums, then I suggest we start a separate SRFI for this.