I think you want my career, and I want yours. I can't answer all of your questions but I would suggest researching Oceanography, Environmental Management, Ecology, Marine Biology, Geology, any science related field. They are all mentally stimulating when it comes to research and you don't work 8-5. However, you will not as an engineer be required to use your tools you acquired in your undergraduate career. You will only be required to research, understand, and explain.
I, as a recent graduate from the environmental sciences, would like to go into environmental engineering as
1) the job field for ecologists/oceanographers/marine biologists is not as placeable
2) I will only be required to "understand" and not fix. I want to fix, or use the skills I acquire in school to SOLVE PROBLEMS! This is not required in the sciences I am describing. I would like to research, link clues, gather information and use this information to come up with a solution. This is what I am best at. It is debilitating to not be able to do something when reading about an invasive species tearing up the ecosystem. As an ecologist, you're not inventing anything to prevent this invasive species. As an engineer, you can design, draft, create the ballast machinery to insert into a ship. And put your label on it!
3) Engineering an interesting field because it is applicable. You can apply your skills and do hard work. The other sciences are about knowledge, understanding, and researching a tiny small part of the puzzle. Often, thousands of other scientists have already done so and published what you wanted to publish.