I ran a simple test to see how using the flat beater attachment would work at speed 6 for a good part of the mixing and initial kneading process. I intentionally used a fairly low hydration, 51%, along with oil at 5%, for a total of 56%. The flour weight was about 191 grams, and the final dough ball weight was about 302 grams. After placing the water, salt and oil in the mixer bowl, and stirring to dissolve the salt, I gradually added the flour and IDY mixture while the flat beater attachment was operating at speed 6. I kept this up until I saw that the flat beater attachment was clearly starting to struggle. So, at this point, I stopped the mixer and calculated how much of the flour and IDY mixture it took to reach that point. It was 73.2%. I then ran the mixer at speed 2, with the flat beater attachment still in place, and gradually added the rest of the flour mixture. At a hydration of 51% and 5% oil, it took quite a while for the flat beater attachment to take up the rest of the flour mixture. After removing the flat beater attachment and letting the dough rest for 10 minutes, I inserted the C-hook and continued the process as you have described in this thread.
I did not experience any machine stress in using the above protocol. But one thing I learned about my stand mixer with the flat beater attachment and the C-hook is that the mixer's practical limit in terms of hydration and oil usage is about 56%. Anything lower than that is likely not to produce a smooth and cohesive dough ball for most styles of pizzas, although it might be fine for a dough that is to be run through a dough roller or sheeter to make a thin crust style pizza. I would also be concerned that the dough isn't kneaded so much that it results in an overly elastic dough in relation to the intended fermentation time. I have been aiming for a one-day cold fermented dough that is not overly elastic.
I hope to repeat the above experiment again sometime soon, also with a low combined hydration and oil usage to see if the method described above can yield a one-day cold fermented dough with good extensibility. However, that said, I am fairly confident from what I have seen thus far is that the results will be a fairly robust dough ball with good strength.