Hmmmm... Very interesting. For what it's worth... The TTK 1655 looks to have the more correct dimensions at the dial/crystal/bezel, as the genuine dial/crystal are about 1mm larger than that of a 1680 or 1665.
Will a genuine crystal fit? My guess is... Probably not. If this is anything like the vintage 1675 MBW rep (which also uses a modern GMT case), the crystal is actually pressed/seated inside the case lip, as opposed to fitting over the lip a la 1680/1665. So, I'd say that a gen 116 probably will not fit (though seeing the watch with the bezel removed will help answer that).
As for the movement... Fitting a gen 1575 might be doable- Like the MBW 1665, it probably requires a little internal milling to get things to line up correctly.
As for drilling the lug holes... I'd say that's doable as long as the right equipment is used (i.e. drill press with the right bits). You may want to check with Ziggy as I believe he is set up to do the job right
All in all, this could be the basis of a very nice project watch...