@dansup c2s is simply impractical, too. Both on the client and on the server.
On the server, you have to merge two disparate streams (feed and notifications) into one inbox.
On the client, you have to split them back apart. You also have to load a lot of non-optimized stuff from different servers. You just have to make lots of requests to do simple things, and now imagine all that on 2G.
I can imagine a "minimal" server that implements c2s but almost no UX of its own though.