I do think he'd be an ace shield to the back four if he was played alongside Gibson. Perhaps Newcastle's goals wouldn't have happened with his aerial presence sitting in front of the back four. We'd concede less goals, BUT we'd probably score less based on current evidence. Can't help but think the "it's Fellaini's fault Jelavic isn't scoring" argument is a myth. Jelavic was slotting for fun last season with Fellaini up there with him.
Safe option would be looking to find a great DM to supplement Gibson and keep Felli terrorising defences and perhaps a more risky course of action would be dropping Felli back and looking for someone who offers similar bossness to Mo behind the striker (nearly impossible, really). Barkley might not be that man. Probably not here anyway so we're looking at a pretty expensive purchase.
Nearly impossible ? I'd rather have Mirallas there all day.