I'm assuming the 3 sides is to make it different to the usual 2 side deathmatch. I see it as a possible continuation of ARMA's team setup that has proved popular.

I can see a few rage-quits from being constantly shot whilst parachuting down

I'd say this will give people an incentive to do halo jumps after you get killed.

Please note that there can be a team with less than 10 players depend on the matchmaking situation.

Perhaps this will mean less randomers, but then it says

You can invite up to 9 players from your friends list to your party before jumping into game.
The rest of team slots will be filled by auto matching system.

So I wonder if you join the matchmaking as a group, you stay as the group, but if you join as one, invite your mates and only two turn up, then your team will be "given" randomers?

Weather is locked at “sunny.”

I wonder will this be changeable if this "event" becomes a permanent option?