“recently modified” hack

Hey. I wanted to be able to see posts that had been “recently modified” as opposed to the date posted. This way I can add entries out-of-order, but still advertise them on my sidebar.
I hacked the get_archives() function to add a recentlymod option. You can see the following function call in use under “Recent Posts:” at https://dannyman.toldme.com/ :
get_archives(‘recentlymod’, 7);
The hack is available at:
https://dannyman.toldme.com/scratch/wp-template-functions-general.diff
Personally, I would like WP to have an admin feature to distinguish between post_date and post_modified … a toggle I could set somewhere to ensure that my RSS feed was behaving as “Recent Posts” does.
I would also like my hack to be considered for inclusion in to WP. Anyone wanna drop me a quick link on how to pursue that? Or is posting here the right procedure?
Thanks,
-danny