I should add I own two 'small' and one 'large' metal Witnesses.
The two small were both originally bought in 9x19, and while one remains a dedicated (and custom) 9x19, the other 'small' frame does duty also in 9x21, 40 S&W, and 41 AE.
The 'large' frame was bought in 45 ACP, and back in the day I also ran it in 38 Super.
I often consider re-topping this with a 40 S&W longslide......
Or you could just start with their 10mm version and add tops as needed