Agreed. We look light at the moment because our only fit, senior CBs are Otamendi and Mangala. Replacing Mangala with whoever doesn't improve that squad depth.
Sorry but that's a ridiculous thing to say. First "We look light because 2 players in that position are injured". No shit. That's the same at every position at every club.
Secondly "Replacing Mangala with whoever doesn't improve that squad depth" but Stones will be back long before we add another CB, so that will never be the case.
Stones-Otamendi & VVD, plus Kompany and a youth project like Tosin for small cup games is plenty of depth at CB for any club. Mangala could take Tosin's place in that line up, but why would he want to? He's 26, he won't want to be 4th choice for league cup games or dead rubbers.