I don't think we can have Sigurdsson at 8, Zat. You know I'm a big fan but playing him there leaves us exposed, and I don't get this idea he has the passing range to play deeper. He's better further up the pitch. In a flat three I think he could work as his effort levels mean he'll get up and down.
Bernard has hardly ever played 10 at Shakhtar. I do think he could play there, but he seems more suited (in the PL at least) to the left, with more space to operate, especially on the counter.
The answer to then get Bernard in the team would be to move Richarlison central, as you say, but as I think
@davek pointed out in another thread, Richarlison has been thriving on the left and Silva's system seems to revolve around him being in that position with freedom to roam.