As someone who built Lego complications before
By: skyeriding : February 13th, 2017-04:32
I can say that minituarising the construction would be a tough feat.
If its simply a scaled model of the watch and non-functioning, then getting the dial symmetry down in lego and the basic case shapes right would need a huge model to obtain that resolution of detail. Lots of curved pieces and SNOT techniques to be utilised for sure. A Gondolo for comparison would be significantly easier to shape since its rectangular, and case shape can be relatively easy approximated by existing curved Lego pieces.
If its a working model of a complication, there are many engineering issues. To begin with, Lego gears are prefixed in certain multiples of teeth, which means only certain gear ratios can be achieved practically (unless some complex, novel methods are used). For instance, a date mechanism requires 31 toothed gear but Lego only manufactures 32t gears. As 31 is a prime number, its not practically possible to achieve this via any combination of Lego gears unless you use differential gears.
However, there are various Lego creations of working Clocks and escapements on YouTube to start with, as reference.
Regards,
skyeriding