While it MIGHT be possible, my 2 cents would be to simply skip it. What external hardware are you trying to use, and(more importantly) is there not a plugin that can do the same(or better) without all the hassle. Now if you have a rack with some real Pultecs, a Fairchild or some Distressors, I can see the appeal, but considering the hassle, and how good plugins are these days......
The crucial setting for hardware inserts is that any insert must use a matching pair of output&input to work. and, given that the X32 inputs are Mic-level, and most hardware is LINE level, that makes it tougher to get proper levels coming back(and you only have 16 hardware outputs, unless the AUX outputs can be enabled in the IO setup page).....just sayin'
