Remaking an unknown or failed film would be of course the best idea, but that rarely happens. Mostly remakes want to cash in on the reputation of a classic.
But Mag 7 is a story you can remake and vary without necessarily be compared with the original. And it is a less personal stuff, and not linked to an individual director.
That a remake of Mag 7 will add a new idea or perspective to the story, something that would give the remake another value than making money with it, is possible but not likely.
And I doubt that True Grit was less well known than Mag 7 when the Coens remade it, or better made a new film after the novel. And it is also still not a realy dated film, not more or less than Mag 7.
Actually for me Hathaway's True Grit (8,5/10) is much better than the one by the Coens (only 6/10 at the moment), and also much better than Mag 7 (6,5/10).
And I was disappointed by Mag 7 when I watched it for the first time. But I see it more positive now, still all earlier westerns by Sturges are better.