Flag friends

Have a look and if the theming functions cannot be here, can you give me some clues, cause I don't see any other way of doing it.
features:
- "Add friend" button on a user profile page, in the action block provided by wsuser module. Add the user being viewed to the current user's friend list. The button is a flag provided by Flag module.
Css classes big, rounded,dark are added to the flag link so it's themed as the other buttons.
To do that I had to change the html code returned by the function flag_create_link of the Flag module . It's not the proper way to do it but I haven't found another way to add classes to a flag link.
- "Friends" tab on each user profile page displaying the user's friends list (if the current user has the right to see it) through templates/view_friends.tpl.php. 
- permission to see other member's friends.
- Link 'My friends' on the welcome block on the front page.