Here is the implementation for call-with-package-renamings (see attachment).
I also attached its test case. I successfully tested this on ccl, scl and clisp.
The run-tests.sh script didn't work for me with sbcl (conflicted with my system settings), so I skipped that...

Best,
`bg`

2011/10/17 Faré <fahree@gmail.com>

> I don't see how can you manipulate things by defining subclasses of
> cl-source-file.

(defpackage :my-system-system
 (:use :asdf :cl))

(in-package :my-system-system)

(defclass my-cl-source-file (cl-source-file) ())

(defmethod perform ((op compile-op) (c my-cl-source-file))
 ...) ;; wrapping!

(defsystem :my-system
 :default-component-class my-cl-source-file
 :components
 ((cl-source-file "package") ;; override the new default, so this one
isn't wrapped!
  (:file "macros" :depends-on ("package"))
  ...))

> I have to admit that I don't understand how components are created in asdf.
> My best guess (by looking at the class-for-type function) is that everything
> defined in the defsystem by :file and having .lisp extension becomes
> *default-component-class* which is cl-source-file.
>

Yup. ASDF is really straightforward. Especially after all the
refactoring we did for ASDF 2,
for the only way we managed to make sense of the code we inherited was
to simplify it.
See also the article Robert and I wrote on ASDF:
http://common-lisp.net/project/asdf/ilc2010draft.pdf

> And I neither want to introduce a new syntax next to :file, nor change my
> lisp file extensions to something else.
> So I don't see how your components can become subclasses of cl-source-file
> at all.
>

Doing it with the new :around-compile feature, it would be:

(defun my-package-frob-hook (thunk)
 (call-with-package-renamings
    '((long-name-1 shrtnm1)
      (long-name-2 shrtnm2))
    (funcall thunk)))

(defsystem :my-system

 :depends-on ((:version :asdf "2.017.18"))

 :around-compile my-package-frob-hook
 :components
 ((:file "package" :around-compile nil) ;; no frobbing around this one
  (:file "macros" :depends-on ("package"))
  ...))

—♯ƒ • François-René ÐVB Rideau •Reflection&Cybernethics• http://fare.tunes.org

The reason why we must be tolerant is NOT that everyone is as right as
everyone else. It is that no system allows to reliably distinguish right
and wrong beforehand. Only by having the right to err can one have the
right to be correct. The attitude of toleration is thus to let the fools be
victims of their own folly rather than of ours, as long as they in turn
do not impose their folly upon us.
               — Faré