Short version: No
The 550 has a maximum size of 13*19.2 and cannot be exceeded without someone re-coding the firmware.
The Fiery supports only what the printer does, so after you hacked the printer, you would then have to hack the EFI Fiery.
And then it would almost certainly in theory pull the paper, only to end up with a paper jam.
So I have a theory that it should be possible to have a max width (simply because the tray isn't wide enough) but the length of the paper can be set to a large size.
The Xerox Color 500 allows to print a SRA3 paper size (320 x 450mm or 12.6" x 17,7")
I have created a test document that has a width of 320mm / 12.6" and a length of 1000mm / 39,37".
The Xerox Color 500 contains a Fiery Server and let's me change a ton of different settings.
In the Fiery settings I can add a custom papersize but only to a max length of 488mm or 19.21"
Can anyone tell me if there is a way to increase this max length size?
I am aware that I shouldn't go and duplex print because that would be an issue. However if I print only one side of the paper it should be able to print a larger size.
Hope this makes sense and is possible.