This is one of those times where I feel like you are being a little intentionally obtuse.
Be that as it may, what i mean is that games without story focused mechanics proceed naturally with things happening because of choices and die rolls and things. And therefore the resultant "story" is more...
Another one I have always wanted to do is run a grounded, realistic game and then have a Terminator appear. It goes from a heist or murder mystery to a slasher film.
I think he would be a Battle Master. The fact that he has tons of "tools" at his disposal suggests something that lets him make decisions on the fly, like maneuvers. You give him a criminal background to get access to stealth and thieves tools, and include Investigation as a proficiency.
The argument about Grimdarkness was built around the idea of whether Scars were Grimdark enough to be "better" at it than 5E. But all of that was personal opinion. I don't think it is fair to classify that side discussion as some sort of flame war.