Daydream would actually make a good studio name, but no, this is just me musing over the delusion of being a game designer. In this instance focusing on the sudden boom of the Battle Royal genre, made popular by the likes of PUBG and then seemingly improved upon by Fortnite.
If I could design a battle royal, one idea I had in my head would be very similar to the usual template, players drop into a large map and scavenge for weapons to kill each other. Except maybe set in a gritty 90s cyberpunk kind of setting, think Quake or Gears of War in terms of visual style. Instead of parachuting in, you drop down to your location via a one man escape pod from space. But the unique concept here would be the ability to combine the weapons you find to make new ones. Basic concept: you could have an energy weapon of some kind and then pick up a shotgun, combine them, and get an energy shotgun that blasts out a wave of energy. There could also be just stand alone parts for certain weapons that need to be all collected. Like maybe a chainsaw or something crazy powerful.
Another idea for a battle royal game would be one set in a fantasy setting. Maybe have the map set on a floating island that slowly crumbles away in place of the usual "blue zone" wall that closes in on the players. Also, obviously, this would be more melee combat focused with players looking for swords and axes and the like, with maybe the rare bow and arrow. But there would also be magic books that could be found as well that would allow the casting of spells. But you need to have the book equipped as a weapon to use the spell, so even if you can hurl fireballs, someone with a battle axe could still rush you and take you out. Visually I imagine it looking somewhat dark and gothic, sort of Dark Souls esque, perhaps. In fact combat probably wouldn't be too dissimilar to when you get invaded in DS.