I actually think these achievements looks decent, never understood why people always whine when there is online cheevos involved, I actually like them, when they aren't that annoying/hard or just stupid.
And these cheevos looks like fun, not that hard, maybe only time consuming. See it as a reason to keep playing the game otherwise.
For the 16player-thingy, I think you only need to play in a game where your team is full.
If you have too invite 16 friends to a party, then it's messed up.