Chances are, the crossover in those B&W's was chosen to compensate for that exact baffle placed roughly a certain distance from the back wall. By enclosing it in a pillar, you'll be doing two things: adding resonance chambers and widening the baffle, which will affect the response.
Now you could damp the resonance chambers in the column and possibly rework the baffle compensation circuit in the crossovers, but that's probably more trouble than it's worth.
B&W put a lot of R&D into those speakers, just enjoy em already
