Sideloading custom firmware onto your PSP will give you the ability to add various plugins and third-party tools, like EBOOT dumps, PSAR decrypters, DRM crackers, and even the ability to both generate and load un-encrypted savedata. Perhaps that sort of thing would open the doorway for future changes. (Some plugins and patches even do tiny things to improve both performance and battery life!)
As for the .PSD templates, the undamaged EG-X Zone Ship is absent. What I can do, however, is export them to .PDN, for anybody who doesn't have Photoshop.
P.S.: I'm working on animated PSP backgrounds, inspired by the animated savedata icons used by WipEout Pure and Pulse. Don't seen to be having much luck...
EDIT: Would it be possible to use this wrapper (combined with custom XML files) to replace the HUD with one from a different WipEout game? The WO64 HUD would be pretty hot as a concave.