The problem is, if we continue with the possession-based style, is it possible to find defenders at L2 level who are comfortable on the ball, good at defending, and up for the physical battle? You'd imagine that players that possess all of those qualities would be playing football higher up the pyramid.
If we insist on signing defenders who can 'play', we'll inevitably end up with ones who aren't the best defensively.
I think we need at least one no-nonsense defender whose job it is to win headers, get a foot in, and boot the ball out when needed. The last player we signed like that was Mark Ellis on loan, and he made a tangible impact pretty much straight away.