My discipline is mostly psychological research, especially as it intersects computer modeling. I could go on about the different projects that I've been a part of, though--many have touched my discipline, and many haven't. You can make a career out of "being capable" rather than out of "being an expert in a particular discipline," though a hint of both is, of course, desirable. If you delve into the "capability" track, an engineering degree can help demonstrate that you are, indeed, capable. And if you happen to also be interested in the specific discipline that you studied--all the better.
Small organizations and entrepreneurship have been where I've been most successful. In a smaller organization, it seems easier to be a part of the "big picture" of the organization itself. There's somewhat of a tradeoff between the flexibility of small organizations and the stability of larger ones, though.