AC4 is a ton of fun. It's good to hear the MP is active because I really enjoyed that in AC Brotherhood and I was looking forward to checking that out at some point.
I wasn't big into Mp since I haven't been able to figure it out. That said, 100% the various SP side missions opens a bunch of mp customization options.
If we hit that bull's eye, the rest of the dominoes will fall like a house of cards. Checkmate.