My idea is add to permission what can allow people create (rename channel to) spacer, now we can’t allow permission b_channel_create_permanent or i_needed_modify_power_channel_modify_name because they gonna create spacer.
It is simple, people without this permission can’t use “spacer” in name of channel.
That can not happen because there is no difference to a channel or a spacer. Both are a normal channel.
Only the Client UI shows a channel like a spacer when a name and permanent and root level does match.
You need to make sure your users only can create a sub channel to avoid that or as you mentioned don’t let them create permanent channels.