Hey hun,
I've been following your threads, but didn't really have anything to add.
Surgery and gastrochisis I do know about.
It really is better for your bub to be delivered via the sun roof with an issue like this. Birth can be very traumatic and can pull on things that in you bub's case do not need to be pulled on and traumatised. They will need to ensure that bub's bowels don't completely disembowel nor dry out or drop bubs temp after birth, that's why they want to get bub covered straight away. A c/section and immediate assessment will prevent (hopefully) further bowel troubles for bub later on in life. Plastic sounds awful but in terms of protecting and maintaining body heat, it's the best thing. It won't be any old glad wrap, it will be specialist and sterilized.
I also think it would be a great idea for you to get into contact with some other mums of gastro bubs. The Royal Children's hossy should be able to put you in touch with a support group or at least in contact with some other mums for some help.
ETA your bub will need some medical intervention. As much as I would love to say it will be your choice, your bubba will need help.