Customization would be huge, in general.
I personally use the 'all cross-type' option; however, having an option for 9 or 11 or whatever number would be great.
And while we're on the subject, if you look at the mapping of the 9 points --do we even know if those are all cross-type?
Also, for the 9 points, why don't they enable the top-most/bottom-most center sensors (which are cross-type)? Why have that rectangle shape when you could have more of a diamond spread (more AF spread... which is what more photographers, in my understanding, who custom select points typically want anyway)?
At any rate, full customization would just allow photographers to use what they need, which would offer an incredible advantage in terms of speed in fast-paced shooting scenarios.