If anyone is replacing Aguero it is Jesus and even at that, Jesus is flexible. People aren't seeing the bigger picture, Pep clearly prefers flexibility within his squad.
I agree.
I personally think Pep is looking at Sanchez because he wants an experienced almost guaranteed 15-20 goal a season player who can play on the wing, just as Sanchez has done for the most part this season with Arsenal.
Whilst Sane and Sterling are promising players, I think he wants someone who is at least reliable in one of those positions to help with the goals.