No-one sane wants to do combustion in a pure oxygen environment. The solution isn't that, it's to eliminate nitrogen and replace it something else. Typically CO2, because you can get it for free and already preheated by recirculating exhaust.
Now what? It doesn't burn, since there is no oxidizer. The only way is to inject some. And since you don't want nitrogen, you can't inject air. So you inject pure oxygen, or something like peroxide?
Sounds expensive.