Sorry for finding another coincedence.  :-))

I swear I did not look into Ithkuil grammar close enough to borrow
this, but only now I found the coincedence:

In the same way as Ithkuil, S7 uses one of its two root consonants as
a classifier.

Is this a common thing to do?

I came up with this idea recently (just before posting the nutshell)
and it solved a problem I had concerning the compounding: I had to get
rid of one consonant in a stem for compounding.  By defining one to be
a classifier, I expect that the rest of a stem (the core) is unique
enough to be recognised in composites.  The head of a composite keeps
its classifier.