How to use functions defined after plugin

I am developing this plugin which uses functions which are now moved to pluggable-functions.php on WP 1.5.1.2. Currently the plugin code executes as it is being loaded and this move in the new version causes undefined functions error.

It is not possible to have my plugin code execute after pluggable-functions.php as the earliest hook I know of is wp_head but I can’t use it for my plugin because page output will have already begun.

I do not wish to redefine the functions in my plugin as currently they are sufficient and I do not want to maintain currency for the functions (think abstraction). What I would need is an action hook that is called before any output is sent.

Anyone knows of such hook or has any better suggestions?