It's worth looking at the current process for getting a GRC.
www.gov.uk/apply-gender-recognition-certificate
Applicants are already required to provide proof of 'living in the acquired gender' but it's just a few name changed documents:
Proof you’ve lived in your acquired gender
This proof must cover the required time that you’ve lived in your acquired gender. It could include copies of your:
- passport
- driving licence
- payslips or benefit documents
- utility bills or other documents of an official nature
All documents should be in your acquired name and gender. The earliest document must be dated before the beginning of the required time.
The indepth guidance that comes with the application form suggests 5 or 6 documents to cover the whole 2 year period.
This is obviously utterly meaningless. You need a GP letter to change the sex on your passport but the other documents can be changed just by asking.
One of the Man Friday chaps managed to change her driving licence to male just by sending the form with no supporting evidence, and then changed it back again just as easily.