Would it be impossible to prise Osimhen from Napoli? They have Raspadori and Simeone so maybe they could be tempted with a big offer. He would be my top priority for our summer window.
If he's not attainable, I guess someone like Shick would be a good option and would likely fit into ETH's style quite nicely. Outside of those two, I don't really know who else would be realistically attainable for us that would actually be a massive upgrade on Martial.
I'm pretty sure he's provided a goal or an assist in every appearance this season under ETH, we just have to keep him fit. Reliability is a huge issue, but if watching the likes of Dalot, Shaw, Rashford, McTominay and seeing their improvement, then I can't see how we couldn't see something similar with the talent Martial has.