I guess the title explains the problem pretty well.

Do you have an idea for a mechanism, which will automatically assign default quota values for every new account created (sort as the skel scheme works, but in this area)?

Now, I am looking for a generic clean solution, not some ugly cron based scripts, or wrapper scripts for creating users. I would also like to avoid any external, unmaintained stuff (like forgotten pam modules, and such). Anything what could lead to overhead and extra work in future isn't really the solution, nor is checking for new accounts every minute.