Gazza M not even stressed about who will start. Remember that Saka started as left back. And we tried him in different places. Timber, Rive, Havertz have all moved around. Across those 5 front positions, Ethan will find a regular slot. As he develops his right side, he could become the new Trossard. Or he could play 9 like a Gnabry. Or be a musiala style left 8.
Likewise, I could see MLS end up as Partey replacement or even a Merino replacement. They both have talent pouring out the ears .