I agree with the principle and that's why we'd have to be careful.
But... what decent, young manager who wants to be the best is not going to have his head turned by better clubs?
If they've got 'ambishunnn' - which is what all of our fans want us to have - then ultimately you can't have someone who is ever happy to be where they are until they're at the very top.
Look at Guardiola, who dumped Bayern off because he knew City were wanting him.
Going on your basis for a 'passionate, hard working' manager, then I'd go for someone like Dyche. But let's face it that's not going to happen - even though I am a big fan of his and I think he could take us forward. Another option would be Eddie Howe, but he reminds me of Martinez.
If Fonseca came to us from Shakhtar, it'd be exactly the same risk as with Silva anyway.