Do you think there's any chance that everyone could have managed by the end of Week 6? I think this would add to the show as most people remaining at Week 7 would get to manage again. I think the team structure and people getting to manage 3 times affects this. I just thought of this as Leah and Tom won the process having both managed once, Leah pretty averagely and Tom really badly in which they had to be appointed and Ricky did it 3 times(considering the 11th task) with a strong individual performance but was let down by other people in his team. This makes me think Ricky was the most credible and deserving winner in new format.

It would depend how many people were fired without having been Project Manager. Usually there are two or three people who that applies to.

The only adult series where every candidate got to manage was Series 2, which had 14 candidates and everyone had managed by the end of Week 7. Everyone in Junior Apprentice Series 1 also got to be a Project Manger, and as there were ten candidates and only five tasks (not including the final) everyone got only one shot at it.

Series 9 was unusual because by Week 7, Alex was the only person not to have managed (would have been Rebecca as well, but she was fired the week before) but still wasn't chosen by his team for two weeks.

I've been thinking some more about this. Under the current format of twelve episodes and sixteen contestants, if everyone was to be Project Manager it would take up until the end of Week 8 at least before everyone had done it (possibly more than that, if anyone was Project Manager a second time before someone else had had their first go, which hasn't happened that much but has a few times).

I've worked it out, and if in the first five weeks everyone who was fired had not been PM yet (which is possible, but statistically extremely unlikely) then in Week 6 there would be only one person left who had not done it. This is assuming that there haven't been any double firings.

Does it not work if 4 people who hadn't been PM get fired by Week 6?

Yes, that would work. It's just really unlikely that that would happen, because with two Project Managers per week it very quickly gets to a point where most people have done it.

There has never been a series where more than three people haven't been PM. Three has been the maximum.

Complete list:
Series 1 - Adenike and Miranda
Series 3 - Ifti, Gerri and Sophie
Series 4 - Nicholas, Shazia and Lindi
Series 5 - Anita and Majid (and Adam technically, but he dropped out before the series started)
Series 6 - Raleigh and Joy
Series 7 - Alex and Ellie
YA2 - Mahamed and Ben
Series 8 - Bilyana, Maria and Michael
YA3 - Max and Amy
Series 9 - Sophie, Uzma and Rebecca

Incidentally, there has also never been a series where only one person didn't get to do it. It has always been two, three or zero people.