Geneshift (also known as Mutant Factions or Subvein) is a top-down shooter with some seriously good action that's currently in Early Access and the developer has decided to add a Battle Royale mode.
Initially, I thought this was a joke. However, it's very much a real thing. The developer put up this gif (converted to video for small file size) on Reddit and it seems to have been a big hit with users:
The way it will work is much like other BR games, with you starting off in a random location as you scavenge for weapons. It will have multiple rounds and when you die, you respawn as a zombie. If you kill a player as a zombie, you get another life. It's going to be faster paced than others, with each round only lasting around two minutes so there's a lot less waiting and walking around. You can read more about it here.
When it comes to more games adding BR modes, I say the more the merrier because I love the idea of it and want to see how more developers add their own unique ideas into it.