An acquaintance once landed a contract to clear up a gold mine site after shut down. He bid super low for it, the only condition he stipulated was it be left in the condition in which he had inspected it, something like that.
The operator immediately gave him the contract, and he immediately gathered up all the dust from conveyor belts etc sifted through it, separated all the left over gold inside and sold it.
Set him up in a big way, the idiot operator tried to take him to court to claim the gold as theirs, with no success.
So yeah, sometimes there truly is gold in that there dust.
Lefty friendly, i would assume your interests would align with trying to help the common person, and climate change adaptation.
Your stated experience, and interests sound varied, and present you as a highly active person.
Combining these things in my mind i instantly thought you should get into food system adaptation for a warmer more volatile world. Where people could really suffer horrendously with climate change is if food production systems break down. We need smart people, willing to try new approaches in that system. Farming where i’m from is bed of roses, and a lot of the skills you listed farmers here would likely use, so its probably the same/similar elsewhere.
So specifically i’s thinking organic farming, or permaculture, or perhaps a more scientific route such as propagation of new tougher varietals.
Logistical needs are also important, the amount of energy used to transport food must be immense and so that could be an avenue you could go down marrying your comments about mechanical engineering to the idea of improving the worlds food production systems.
Good luck with your ongoing career, whatever you decide.