The CAA will make no effort to defend the actual age. They will simply point out that at present it is an EASA regulation, so outside their control. Even if we leave EASA next year and they reviewed it, any change would be (like the Australian rule mentioned above) only valid in the UK since the age limit is an ICAO standard. I don't know of any airlines that only operate domestic flights, so not much opportunity for jobs even if that happened.
So basically he's just wasting everyone's time. It probably says most about his lawyers that they haven't told him that and are happy to take his money.