[development] hooks after hook_menu is called, but before page rendered

I'm in the process of updating taxonomy_breadcrumb to work with 5.0 and as part of the upgrade I'm making a few improvements to the module. I want to have an opportunity to change the breadcrumb trail after hook_menu has been called, but before the page is rendered in the theme. I'm not able to find any way to do this. Any suggestions? It seems as if I need a hook added right at the end of menu_execute_active_handler() in menu.inc, after call_user_func_array (but before returning). Am I missing something? How can I have a function in my module execute after any other hook_menu's have been executed? In the rare case I'm not overlooking the obvious how to I begin the process of trying to get a new hook added? Thanks! Craig