I don't know... you can theoretically get to 40+ ppm with pure O2, and I have heard that there's the possibility of oxygen toxicity. In practice I'd be much more worried about affecting the flavor profile than harming the yeast. Pitching rate, temperature, and aeration are all factors that affect the flavor of the final beer, and adjusting any one will change the result. I would be very careful about using too much oxygen in any beer that is supposed to derive a lot of character from the yeast.
Oxygen toxicity exists, it is just not an important consideration for homebrewers. Even at 40+ ppm, that level will start dropping within minutes of adding the yeast. RDWHAHB
As for it affecting the flavor profile of the finished beer, like you pointed out it is just one of the things you can manipulate to get the flavor profile you want.