How to sharpen knife with chunk missing?
Grinding the blade down that much would potentially change the shape of the blade. Due to the full depth bolster you would have to either try to reshape the bolster as well or create a blade that tapered very differently. 
The knife is an Oxo Good Grips 8” chefs knife which sells for around £20. It’s difficult to see that either of your options would be as effective as replacing the knife, unless it has sentimental value.