If you make anope do this, it would cause desyncs I think..
If the last user leaves the channel anope expects it to be empty (it doesn't see its own clients as users whereas the ircd does) which means it also expects all settings to be cleared...
It would break for example the unban command... if the last user leaves anope would think the channel to be empty and all bans cleared... therefore if for example the owner got banned he wouldn't be able to get in since unban would say the channel doesn't exist.
To keep a channel open it would ideally have to be done by a client that isn't local to services..
[Edited on 17-3-2008 by Viper]