I am a joiner too (a great thing to be), and have dabbled a bit in watch boxing, but I came to the conclusion it would be hard not to charge too much.
I didn't take it forward, and I like your approach
Here is the watch box I prototyped. The handle is laminated (by me) sapele and oak, the box oak, the lids are automaotive leather offcuts recycled, bonded onto 3.6mm ply for shape.
I was going for a high end toolbox look.
I made some very effective watch "pillows" that were actually stands, a base, a side and a top all in wood, with a foam (cut precisely to size bought off Ebay) back on the watch section. It holds watches very well, but I suspect that sandwiching the wood in foam would be better.
Here is how they fit into the box (lids removed as display mats, and drawer open)
The drawer (for straps) is a bad idea, it is complicated and straps (which are not flat) kept getting caught in the drawer.
The idea was also that if the owner decided he didn't want 10 watches any more, he could still use the box as a carry round toolbox (you can see the coin magnets in the central wall here, that hold the lids in place).
Some possible easy value added suggestions, if I may?
Veneered birch ply for a feature panel (lid?) may add significant value (oak, ash, maple and sapele are available).
Alternatively, making the lid from a single solid hardwood board may add more too.
Also, dying the birch can be very effective, rather than painting, as the grain is still visible.
I did a hardwood table football table, and the pitch was green-dyed ash. It looked fantastic.
Finally, branching into another mateiral can help, I used leather. The leather I had to hand was black, but a deep brown suits wood very well, and I would have used that if I had it.
Good luck
Dave