The thing is, whilst we do have a fair number of central midfielders on the payroll, many of them are consistent underperformers who are wildly overpaid. Provided we could bring in better replacements, I suspect most of us would be content to see three of Davies, Delph, Gomes and Sigurdsson depart - look at the rage levels on here whenever one of those is named to start in the middle (not Delph, obviously. If he were named to start, most of us would faint and the club's medical staff would be arrested on suspicion of witchcraft).
The proof of the fact that only Allan and Doucoure are suitable for Prem-level competition is that the very moment we lose one of them, we start to struggle, to the point that we have to alter the way we play and change our shape. When BOTH of them are missing, we lose. This isn't to say that the other positions you mention aren't needed BUT in the ongoing attempt to trim the wage bill (and thereby facilitate the purchase of better players) I bet the club will be looking to shift another big earner out... the only part of the squad where we can still do that is in CM.