I can safely say that no airline would consider a trainee at 40+ a safe investment, and i would seriously doubt that a pilot who has experience would say otherwise.
I think you should phone an airline, such as BA, and ask them what they think, get a professional opinion, i would think that your best bet maybe air taxi on turboprops etc. or eaven general aviation (socially).
good luck, don't mean to sound cruel, but the money which you would be putting in, you need honest opinions!