The pebble might be a good option though, not only is the os now open sourced but there is apparently someone trying to build new watches.

Once you get out of the hobby space, Hardware is a tough business, and there are a lot of people that would benefit from a solid solution that won’t be up for tinkering.

You might also find that there are Chinese manufacturers with white-box watches that might be running common chips like the nrf52840/832. I certainly see a lot of apparently identical smartwatches around 30 dollars that are marketed under different brands. Those might be a better direction if you are looking at a broad market.

OTOH, once you get away from the supportive and nurturing maker environment most of the fun will leak out, so depending on your motives, you might want to stick to your solution - which looks pretty great to me, even if it might not be as simple to scale production.

Best of luck with whatever direction you are looking at. By the way, you might try a resin printer if you are going to be doing any production in house. For larger multiples of small parts they are crazy fast and the finish is pretty great.