This WAS the original discussion
I said (to summarise) - 'we;re going to have to find/do
something with Sancho OR accept he's a £173m bust'
At which point you said (to summarise) - 'sell him'...and my last two/three posts have been focused on why I believe that's not an option.
To answer your question about what makes me think he might come good....well....personally, I don't think he'll 'come good', in the sense that I don't think he'll ever be a starting XI player for us, IF we want to compete for trophies.
He's not a total bust though, he has some positive attributes. He is technically very good, he sees a pass, he can score the odd goal, he's good in tight areas....so again, going right back to the very beginning...I'd like to see us at least try and coach him into a #10. At least at #10, his lack of pace might not be such a major issue.
You keep referencing Martial....and we have had precisely the same problem there. We give these lads massive wages before they have achieved anything and then no club can afford to buy them when they don't reach their potential. Had we given Sancho £175K, for example, or even £200K, there might have been hope. At £350K we have absolutely no chance of moving him on, we're completely stuck.
Same with Martial...if he were earning £125K per week and not £220K (or whatever), some club like Newcastle, Spurs, Villa, Everton, Sevilla, Dortmund etc....would have bought him by now...but nobody can or will pay the outrageous salaries we pay and players aren't stupid...they won't tear up massive contracts to move to 'lesser' clubs on significantly lower wages.