You might try talking to this guy, he added an outside shower. More or less the same concept.
https://www.jaycoowners.com/forums/f...ods-65579.html
If I were doing this, First I would request a copy of my trailer framing plan from Jayco. Then I'd go to a Jayco lot, find a trailer with the door size you want, and ask service to order you the parts for it.
A bit of time with a saw, soem careful re-inforcement of the opening, probably adding a 2x2 frame around the new opening, and a bit of time with dicor.