I agree with your definition of a tool watch, even if there can be several, for example: a rugged watch that can be used and abused, but strong enough to keep good time and looking good. Like a Seiko Willard, worn by nothing more than Naomi Uemura in his explorations:
And I wouldn't hesitate to wear it for an evening date with Ursula or Anne Hathaway!
Or like this grand son:
But I wouldn't qualify them as elegant.
Then when we go into the ages, it looks like tool watches were smaller, slimmer and perhaps dressier, like my Movado Kingmatic, with its water proof Borgel case, which were considered tools in their time, but now we see as dress watches:
Or what about this small JLC from 1940's, a real tool watch in its time maybe?
Or this Angelus Datalarm, probably worn by a traveling agent just for waking up at a different destination each day in it's former life:
So there can be many tool watches out there! It is fantastic.
Now, going into the one watch for all circumstances definition. For me, it has to be a diving watch just to be waterproof, with no more complications than the date, and it has to be elegant enough to wear it proudly and enjoyably at a formal event, so my modern favorite, and you knew it was coming, is my Planet Ocean first gen. I wore it at my wedding, I wear it when playing with my son, and of course I will wear it some day on a scuba trip to some beautiful beach. It was bought after a long deliberation, taking the Rolex 16610 as the reference for the wear it everywhere, do everything "elegant" diver. The Omega won, and I haven't regretted having preferred it over the Rolex every single day! So here's my winner:
Oh! And the plus over the submariner is that lovely domed anti-reflective crystal!
What tool but elegant watches would I like to buy? The Vacheron Constantin Overseas blue dial in steel, or the dual time in titanium, the Rolex 116600 seadweller, or why not? A nice vintage 1675? Who knows what time will bring?
Thanks for the chance to share out thoughts about this interesting and never ending theme.
Best regards.
René