From what I have read from many different sources, 1mm thick is not uncommon for a Torres guitar.
Many, if not most of his guitars still in existence have been re-finished, often more than once. Aggessive sanding in these operations may be a cause of this extreme thinness, as mention in the recent article on flamenco guitars in GAL.
Other causes may be that Torres had limited access to decent wood, and may have had to work with thinner boards, or was trying to save by resawing to the extreme. Remember also that concert pitch was lower in those days, so string tension was less than today with higher tension strings, which in turn may have influenced Torres in his decision for side thickness.
I guess if you are trying to make a perfect copy of the original, then you should follow the plan. This of course, would also mean using gut strings and using a lower concert pitch.
If however you want to make a more modern guitar with a specific Torres as an influence, then maybe you should make your sides a little thicker (1.6 to 2.8mm perhaps?). It will certainly help the instrument maintain its shape and condition over the long run.
This is a compromise that only you can decide on. Just remember that you should claim that it is a perfect copy of a Torres guitar if it reallly is made to its precise specifications, or that it is a Torres inspired instrument if you take some liberties. I personnally find it a bit deceiving when one claims to have made a copy when in fact it isn't. Then again, maybe I am just a little too tight around the collar...
Good luck,
Pat