Thing being ... mod_perl let you do most of your configuration in code years ago. Yet I've never done that, and nor have the vast majority of mod_perl users I know (and bear in mind these are people self-selected to already like writing perl, so language wars probably don't make a lot of difference to my argument :).

Configuration isn't code, and I don't really think trying to make it such is necessarily a good idea - I suspect it seems superficially attractive to developers but with my sysad hat on it really doesn't seem wise.