Have you seen the physical size of the 5 speed? Apart from the fact that it is made to bolt up to a V6, the bloody thing is MASSIVE compared to the C34 box. Not having closely examined the possibilty myself, I cant say for certain, but I can imagine that the trans tunnel would need a fair bit of modifications, shifter position and connection would need to be looked at, you would need to look closely at the departure angles for the front and rear driveshafts, position (and size) of the transfer case, attessa ecu compatibility, the list goes on and on.
this is why there isn't much interest in it.