What has he done in his career? It would be easier to help with a bit of history here. What did he enjoy the most? What did he feel he was best at? Why is he still working and not in retirement?
There can't really be a shortage for more support engineers if he likes that, but if he wants to do more core engineering then of course go for that. Most of the big enterprises should have room for him in many different departments and he might be comfortable and safe.
As for concrete advice: Just go looking for jobs and weigh pros and cons. You can do it on his behalf and bring a few to him for discussion.
Don't be pushy if he's not into the idea and just feels like complaining a bit. Sometimes all a person needs is a bit of acknowledgement and not a solution.
This should not be a question. It is none of your business.