Get a new ID the represents your new identity and the problem is solved. I am amazed you even thought they would accept an old ID that contains totally different information.
This is not possible if he is on the Philippines. Sex change or any form of gender related issue such as same sex marriage is not allowed here.
I think he/she should use his original name and sex to match with his ID since his face might be the same unless he do some face alteration surgery also then his case is very hard to solve.
@OP, What is the response of Stake when you send the proof for the sex change surgery? Your case is peculiar and you can’t blame Stake since there’s a lot of cheater trying to attack them using different method just to bypass KYC.