yes, this sounds good.
Now I’ve found this in 44.018 (par.184.108.40.206.3.1):
The network may allocate a dedicated channel to the mobile station by sending an IMMEDIATE ASSIGNMENT
message or IMMEDIATE ASSIGNMENT EXTENDED message in unacknowledged mode on the same CCCH
timeslot on which it has received the CHANNEL REQUEST. There is no further restriction on what part of the
downlink CCCH an IMMEDIATE ASSIGNMENT message or IMMEDIATE ASSIGNMENT EXTENDED message
can be sent.
So it seems that there is no a strict rule about CCCH blocks definition, except for some scheduling of some basic sysinfos.
grazie e ciao 🙂