It would be a wonderful move for Chelsea of course. But how can they do this now? The transfer window isn't open anymore. If you mean they can do this in January I don't think so. Napoli would never let Osimhen go in the middle of the season. There is no way Osimhen being keen on doing so either.
Besides I'm doubtful about Osimhen to join Chelsea even if he becomes willing to leave Napoli soon. Chelsea can give a lot of money to him for sure but they aren't a successful team these days. Osimhen would rather stay at Napoli whose condition is much better I think.
As far as I know Napoli are working on an extension of his contract on one hand now.
It's possible that it could happen in the summer after the league finishes for the half-season looking unlikely for Chelsea to sign him.
There has been a firm statement from Napoli that Osimhen will not be sold he will remain at Napoli in the long run.
Chelsea are still doubted by many players because this team is always not growing and it must be overcome from management to training, but for now it cannot be said so because Pochettino is still trying to improve Chelsea's performance even though we have not seen the growth.
Reading the article that Osimhen has a clause of 150 million if I am not mistaken, but the agent wants below that, this may reinforce that Osimhen does not want to be sold in the near future.
See Al Hilal's offer as more promising.