In Section 47 of Factories act (Shelters, rest rooms and lunch rooms.)
(1) In every factory wherein more than one hundred and fifty workers are ordinarily employed, adequate and suitable shelters or rest rooms and a suitable lunch room, with provision for drinking water, where workers can eat meals brought by them, shall be provided and maintained for the use of the workers:
But as per your requirement as permanent rest room for designated employees; my view is little different:
Factory is licensed for manufacturing process (as per section 2k) and if you allow your in permanent rest room then within that factory premise factory act will be enforced. (This may trouble in case of accident).
You may choose that area for permanent rest room that is not covered under factory license.
Seniors may input their views.