It's clear that Ruben Amorim needs to completely overhaul the depth of Manchester United squad, not just the front line. Many of the players inherited from Ten Hag don't fit the formation that Ruben Amorim is bringing, so it's no wonder they're struggling right now. Regarding Ruben Amorim movements in the transfer market, Manchester United can actually recruit any player they want, not just Osimhen, but clearly, securing a Champions League spot would make their steps much easier. Not only as an attraction, but also as a source of income that can smooth out their plans. Releasing Rashford, Antony, Casemiro, Hojlund and several other players is another way they have to rely on to get income.
United may have to do that. Release some players who don't really fit Amorim's style of play, then replace them with players who fit Amorim's desires. Only, if later next season after all that has been done and it turns out that Amorim can't give what the club wants, it will all just be a longer bad story for United.
But you're right, getting a ticket to the Champions League will be an added attraction to make it easier for them to get the players they want.