ENIGMA is an effort to merge FIST with GUMSHOE for more mystery focused games. It seemed a bit unwieldy as I see them as very different systems, but your mileage may vary.
There are still plenty of ideas worth considering even if you don’t use the investigative specialties. The “Insufficiently Trained” section has ways of delivering clues to your agents and that’s where things get gonzo. Sassy robot partners, demonic familiars and psychic powers are just some of the ideas that would fit in with any mission or team.