Rashford is streaky, he could go back into his shell like last season and we would be fecked. Remember this isn't his first breakout season, he had it before but didnt build on it but now he is matured having overcome last season's adversity and playing well in a better and happier team so maybe this time he will stay in peak form.
I know we need to sort out the midfield but I'd sooner have the top striker in now and make Sabitzer permanent for 20m odd. We have Eriksen to come back but I feel that Sabitzer in top form could provide us that balance alongside Casemiro and make us more physically imposing in midfield. Eriksen can start those matches against parked buses and Sabitzer comes in for the more combative ones. Then at times Bruno goes to the right and Eriksen plays in the hole. Perfect balance.
If I had a choice I'd choose Kane over Osimhen, the long term benefits of the latter notwithstanding. Why? Because Kane, as you said can feed Rashford whilst scoring a ton himself. Osimhen, Rashford and Bruno would be too many inconsistent passers in the front four for ETH's liking hence why I see him going for a younger striker to build up banking on the Rashford goals in the interim. A Martial type of striker would he ideal because he'd bring the best, in scoring terms, out of both Bruno and Rashford.