Doctor. Still want to explore "systems" to diagnose issues and build plans for improvement.

When I was 45, I did briefly consider making the switch

As a med-school dropout, in his early 40s (left medicine two decades ago), I cannot even imagine having enough energy to even apply for medical school. At least in the United Hates of America, this is my jaded perspective.

I became an electrician, instead, with stints IBEW and self-employed residential. Lots of money-making opportunities, but lots of unlicensed competition from handymen that "know just enough to be dangerous" — most customers only care if the light turns on, not that it's long-term safe.