I long thought about this and did it for a few weeks. I have many mechanical watches and I love them. Apple Watch on right hand, unpaid down on discreet black sport band or leather loop to make it look like a bracelet. Mechanical on left. Gradually I found myself relying on the Apple Watch and started wearing it as my only watch on the left.
If I were to do it again, I would look at these bands - look very discrete (like wrist bands with a soft fabric) and if you wanted to, very easy to rotate the Watch to face you without having to unclasp the band:
https://etsy.me/2jwjVbU
For anyone amused (or bemused) by OP, this concept is actually a ‘thing’. Even some mechanical watch manufacturers are aware people want the utility of their Watch without giving up their mechanical:
Source:
https://www.nicogerard.com/pinnacle