I'm sensing here that the bass cab is somehow colouring the bass tone to some large extent; enough to 'justify' adding it to the bass tone from a post-pre or post-power amp signal into a suitable DI. I would gather from this that this specific colouration is both wanted by the bassist (and, by extension, the band...), and is a constant throughout the performance. For my part, I find it strange that one would want the same bass tone for the whole length of the concert or event. It certainly wouldn't be usual for function bands, where a wide variety of styles is the norm. If the cab itself is, indeed, such an important part of the tone, it's going to be very difficult to change for another, as most cabs, whilst having maybe their differences, are designed to colour very little; not enough to make the sound so distinctive as to be essential, I'd have thought. I may be wrong, of course, but I find the notion rather odd, that's all.