If Amorim were to keep Onana, I believe United's focus for the winter transfer window would be more on attack and defense. Because it seems that those are the areas that United are having problems with.
If Amorim wanted to make a major overhaul of his squad, that could happen, but as you said, the ideal time would probably be in the summer. Amorim could get a few in this winter would be great. And that would mean there would be a few names that United is ready to let go as rumored.
If Amorim keeps the current squad, I'm not sure United would get a good result either.
It seems that we have quite a lot in common regarding the discussion about Manchester United, but it is actually very unfortunate for me if in fact Amorim really releases some of his players, especially Marcus Rashford. I actually like Rashford more than Garnaco, but he seems to have problems with discipline and often seems selfish. Actually, sometimes Bruno Fernandes is no less selfish in my opinion, but it seems that Amorim will not release this player compared to the other two names I mentioned. Maybe in the winter Amorim will recruit one or two players that he needs, especially if Amorim gets an injection of funds from releasing one of his players. Well, for now there is no choice for Amorim to only focus on the available players. And you are right, because there are indeed some players who are not ideal with Amorim's style and system. So, there will be some players who will be released either in the winter or the summer.