Have you thought of using a De-humidification DOA unit instead of A/C. This type unit uses a desiccant wheel and gas or DX reheat to regenerate the media. Since low temperature is not your goal and you are handling cooling in the space they are more energy efficient than 100% OA DX units. Check out Munters.
to tell the truth, this is for a new building in africa where I can't find supplier. In addition of that, their voltage is 400V/3ph/50hz. I've tried to contact Greenheck and Reznor to know if they supply out there but no answer.
This is why I am asking if I can use standard roof top unit by Carrier or Trane which are available outthere. Can their compressor damage at 100% outside air?
munters, deschamps, AAOn, venmar all make units. if you can utilize the lav exhaust, you could use an air to air heat exchanger for energy recovery, with no air coming into contact with the other, otherwise known as ERV. munters HCU are nice, but pricey.