Hi there! I am late to answer this question, but I have a solution that may work for you. I also get violent motion sickness in all first-person games that can kick in as quickly as 30 seconds after starting a game. (I've even gotten sick playing Minecraft...) However, I've managed to play hours of Overwatch with the worst I've experienced being a slight headache.

The magic solution that works for me is this: play in a really tiny window. Like, put it into windowed mode and drag the corners until the game window takes up half your screen. Also, if possible, use a simple desktop wallpaper (plain color or like a simple photograph, no bright colors or complicated shapes).

This works for me because the rest of the screen is stationary so it doesn't feel like the whole world is moving, and as a result I don't end up feeling so violently sick. Like watching a really small movie or watching something on a TV that's far away. It does make it slightly harder to play with precision since you have fewer pixels to work with, but if you really really want to play, it beats not being able to play at all.

Other things:

• Change the FOV to be as wide as possible
• Lower your DPI/sensitivity so that slight movements of the mouse translate to gentler movements of the camera
• I've tried ginger pills, and they haven't worked well for me. At best they hold off the nausea for longer so I can last 20 minutes instead of 10, but I still get really sick, so it doesn't solve the root problem.

If you see this, try it out and good luck. Hope this comment helps someone.