Well, I don't really want to start another client/server debate, it just ends up going round in circles! But no, it's not possible to do the things mentioned above at the moment, it's all been discussed before. Here's another thread with someone trying to get their head around it as the procedures are not explained anywhere and it's up to each person to find out for themselves that it doesn't work.
http://yabb.jriver.com/interact/index.php?topic=85886.new;topicseen#newBasically, the workarounds involve various combinations of switching to a temp local library, maintaining separate libraries, or using a third-party client/server protocol (i.e. RDP, VNC) - all of which mean
not using the MC client/server functionality.
It is not possible to rip CDs on a client into a remote library, nor to import into a remote library, and people have also mentioned deleting/moving issues. There are also suspected synching issues where changes made on a client are not guaranteed to reach the server. See above thread for an example. I can also imagine that turning off the client after making changes is going to be dangerous.
I'm talking specifically here about a "library maintenance client", i.e. the ability to connect to a library whever it is on the network, whether it's hosted by another PC or whether it's hosted by the PC you've got the client on, and maintain it. There shouldn't be any limitations on functionality and data integrity just because the library is not on the same machine, it should behave in exactly the same way regardless of what library you are connected to.
With regards a "playback" or consumption client, there are also possible issues regarding the ability to control a client when connected to a server, or vice versa (it's a bit vague to me at the moment, but this question has criopped up several times). It seems that to be able to control all MC instances and zones, you actually have to set up multiple servers and switch between them, which is counter-intuitive when you think you've designated a "server".
jmone's diagram is actually a classic client/server model when you break it down into basics and I'd love for MC to get to that point as a multi-platform networked media system but the individual functions need to be separated and client/server issues ironed out before it can become seamless, logical and useable for the average non-techie.