Hey Paul,
If I were a betting engineer ..... or part of the design team at Behringer ....
I might heavily consider creating a DL1608 form factor mixer with X32 sub assemblies. I might pair down the I/O to be appropriate to the form factor, but leave the processing and code base common with the X32 series.
By the looks of the original specifications if the iX16, it doesn't look like this is what they started with (by the number of busses and the number of efx engines for instance).
I could be way off on this .... it is pure speculation