That's an interesting idea. Since the aggregation settings are stored in Drupal variables, and those are read into the global $conf array during bootstrapping, I tried the following in a modules hook_init()
implementation:
global $user;
if (1 == $user->uid) {
global $conf;
$conf['preprocess_css'] = FALSE;
$conf['preprocess_js'] = FALSE;
}
So far this just works :)
Now I'm suspicious - according to my standard experience over the years, if something is that simple on first sight, it will break down horribly sooner or later ;)
But right now the worst thing I can imagine happening with this is that it just fails in situations where for some reason or the other the $conf array gets repopulated during a page cycle, in which case the admin would just get the cached versions again.