My summary of this game Part 2, and a rational comparison to Planetside 2.
TL;DR - Mavericks: Proving Grounds can be interpreted as Planetside / Planetside 2 in Battle Royale format. Planetside 2 has a reasonably-sized community, but the game also came from the same exact developers as h1z1.
In this post I allude to a game made in 2003 that could handle up to 450 players in a single battle simultaneously playing a massively-multiplayer war simulator / MMOFPS with strong military elements. I saw the game on the old TV show Extended Play / Xplay back when I was 13 years old or so. Fast forward about 4 years, I got a job, built my first PC ever, and started playing the game and found it enjoyable as a grind / sometimes exciting push and hold position / take that massive base and push the enemy out type of game. You had tanks / planes / buggies / troop transports (both ground and air), but of course you could never have all of those abilities all at once. The level-up system would give you certification points. You had a set number of them to begin with. There was no method to directly purchase these with cash. You had to grind to get them. You could be a sniper that piloted light planes, ejected on mountains, and scouted the enemy or sniped them while they were waiting for buddies to show up with vehicles. Combat, while somewhat lackluster, was most-exciting in larger engagements where everything got mixed together - tanks, planes, bombers, snipers, anti-vehicle weaponry, anti-air, anti-tank, anti-infantry, you name it, all of it was there at once and that's what made it exciting.
The open world in planetside:
Essentially you play as one of three factions in game - the Terran Republic, The New Conglomerate, or Vanu Sovereignty. Each faction had it's own sanctuary and, aside from color schemes, they were essentially clones of one another. At sanctuary, you couldn't shoot, but you could load out vehicles and customize your "battle loadouts." The three factions combat each other to control the entire planet they are on. there are 8 continents and each continent is a battlefield. Each continent is massive (think equal to isle of dern in size, not detail though). You battle for control of various bases on each continent until your faction dominates a continent. There is no victory condition, just endless war and grinding for level-ups.
I can only speak to Planetside 1 because my stints with planetside 2 were all temporary at best. The combat in Planetside 2 was much better, no doubt, but somehow it just didn't feel the same as the first planetside, so I didn't stick with it. Also I got in to a different esports title at the time and became a paid commentator eventually. I did notice that lag/desync was an issue at some points.
Community in planetside:
Eventually he community came up with slang and propaganda for each faction of the game. NC due to their mostly deep/bright blue uniforms were called "smurfs." The Terran Republic was usually referred to something now deemed "offensive" that I won't mention here, and me and my friends usually called the Vanu Sovereignty "Boogiemen" because they were all purple.
MPG will not be a ripoff of Planetside, so don't get that idea. MPG will be the first real open-world battle royale game. It will take some elements from Planetside and some MMORPGs. We will make the slang, some of the lore, and we will be the community.