You make a lot of good points! I dislike the idea of multiplayer, because I feel it removes a lot of the sandbox elements present in the series.
I don't understand what you mean by "How much of our OCD will take over (me included) and will be bothered by Not being able to change the clothes of any townie(other player's Sim)? Funny at first but not so funny in particular situations.".
I strongly agree with "Maxis, your Simmers don't like you having control (game mechanics and your choices of content) and they sure don't like other players getting control."
I am unsure about "Cliques, envy, strife, backbiting and gossip. Is that what we want the Sim Commuity to become. It goes on enough as it is already and has for years and years. Just imagine the cliques of a multiplayer Sim game."