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Prime with extension tubes and proper manual focus capability, whilst using the focus assist zoom or at a minimum focus peaking.
I can almost guarantee that buying the dedicated macro lens will result in loads of photos where it focuses on the wrong area of the watch. That’s negated a little by the necessary use of a tripod and smaller aperture, but it will still be clear where the point of focus is, and where it was intended.
Depth of field becomes incredibly shallow the closer you get.
It’s very subjective what is a bodge and what is a solution, with photography. Nowadays you are sold a product that is especially designed and marketed to do what you can succeed one hundred other ways.
A prime, plus extension tubes (or even just the filter), may suffer from a loss of a stop of light but you may gain a faster, lighter, more versatile and cheaper solution. It’s a lot of cat skinning.
Edit: also, minimum focus distance of 16cm really isn’t very close at all for that focal length, it’s acceptable for watches, but as I envisage it you will still max out your focal range and be cropping. You won’t get the best of up-close shots of the parts inside the watch.