I think Mbye gets the nod because he's currently playing fullback (and is a decent returner of the footy), has played 6 & 7 and I think his body type and strong running game could lend him to filling in at centre if need be. A few years back when he was at the dogs he may have even been pushed to left center at some point.
His defence in the middle would be a concern but so would Milf's to be honest... and Mbye is a bigger body so that should help with defending in the middle and potentially being a roving middle like we've done with DCE, etc. in the past
It would be interesting to see what happens if we lose a winger though??
Potentially Mbye could do a job on the wing as well... given his fullback background.