I understand that you are proud to have found a solution to your issue but hack the kernel is a very very very very bad habit ! The main reason is that the day you will update your ez instance, you will have to hack again the kernel...
As far as I remember, in the login.tpl file you can put an hidden input called RedirectAfterLogin and its value is the correct URL where you want your user to go. As it's in the template you can generate it...
