I congratulate to the startup idea! And I wish all the best!
BUT! And excuse my critical note, but I absolutely loathe the idea that my company would intrude my personal private life on whatsapp! You know what's the first thing I do when I leave the office? I turn off each and every channel which is connected in any way to my company. Complete radio silence. No email, no hangout, no slack, no nothing. Zero, zilch, zip, nada.
Seriously? You want to answer company surveys in whatsapp? Seriously? I doubt it. I sincerely doubt it.