I missed the last round of Nexus Blitz, so, first impressions for me are this:
Riot employee 1: "Alright people, we need a new game mode, what should we do?"
Employee 2: "5v5 on Treeline?"
Employee 1: "Nah, we had 6v6 on Treeline in the past. Next!"
Employee 3: "What if we worked with Doombots again?"
Employee 1: "We've done enough with Doombots. Next!"
Intern straight out of high school: "BrInG bAcK uRf!"
Employee 1: "Shut up Jhonny. Next!"
Employee 4: "What if we just combined all of the game modes we've made in the past into 1 game mode?"
Employee 2: ....
Employee 3: ...
Intern Jhonny: "That's stu..."
Employee 1: "That's brilliant! Why haven't we thought of that before? Get to work people!"
Seriously though, it feels like everything Riot has tried in the past has some sort of influence here in Nexus Blitz.
6v6 on Treeline (5v5 on a condensed map)
Doombot mechanics (AoE Blitz hook, Loot Teemo/Veigar)
Ascension/URF (large buff on killing streak)
Nexus Siege (sled blows up a structure)
Poro King (self explanatory)
2v2/1v1 (prize fight)
But also a few new things, such as their own version of a Battle Royal, and the Scutte Crab race.
This game mode is nuts, and I'd actually like to see it become a permanent mode. It's a nice middle ground between ARAM and SR. Though, admittedly, Twisted Treeline may suffer the most if it does become a permanent game mode, since it is already struggling.
Despite that though, great fricken job, Riot. This game mode is fantastic.