Your sig is ridiculously large just so you know.
As for swapping headers, try it, the headers have specific data for that particular ROM. It's not a big deal too make a copy and then modify the copy. I doubt you will accomplish anything by doing so however. The headers are fairly specific to each game and the content in them. Most emulators rely on this data to properly know what the code type is as well. There are several microcode 'types' for the RDP.
Which leads us into why things are the way they are. Due to the memory constraints of the ROM cartridge N64 games had quite limited content space available. Of course this required some creative work to port games to it. A perfect example would resident evil 2. A lot of MP3 compressed audio and heavily compressed backgrounds. This was unnecessary in the PS1 version because they had 700megs and unlimited volumes for space, versus 64megs and a single cartridge for the N64.
Cyb