Yeah I have a workaround.
unlockall command still doesn't unlock additional 5 class slots usually gained from prestiging normally.
Workaround is to manually prestige by one level using this command
statsetbyname plevel 1
And going to barracks to unlock the class slots at the prestige mode
And under prestige awards, select extra class slot.
To unlock next 4 class slots, just type in the command
statsetbyname plevel 2
And repeat the steps till you get all the class slots unlocked
Copied from PeterG
