I've taken a look over tha avaliable permalink tags (http://codex.wordpress.org/Using_Permalinks) and i'd like to add one (%epoch% - to reflect the unix timestamp a page was created on) to match my current blog software.
I've taken a look through options-permalink.php, link-template.php and rewrite.php which seem to be where the changes would need to be made.
There are a number of things i'd like to check first tho:
1: Is there a better way for me to implement my changes than altering those files?
2: If I do alter them, is it worth me making a patch and submitting it?
3: Is there anywhere else that i'be missed that I'd need to add the change?