NOTE THIS IS JUST AN IDEA.!!!!
I came up with an idea that just might work..
1.You need 2 memory sticks.
2.On memory card #1 you have the folder called "UPDATE" in the game folder and a real 2.00 update file.
3.On memory card #2 you also have a folder called "UPDATE" in the game folder except you have a homebrew file that is a pbp file.
--On the psp start the 2.00 update using the 1st memory card.As it starts to boot replace the 1st memory card with the 2nd memory card that contains the homebrew file and maybe it will boot up.?>?>!?>>?/ hmmmm....
THis is just an idea and maybe will lead to a better idea.