The "Other Guy" in the Ekko video DEFINITELY IS (a) BLITZCRANK (skin)!!!

Special Thanks to Mr. Tamer (NA) and Spoody (NA) for pointing out more of the similarities than I noticed originally (you can find the orginial post here: http://boards.na.leagueoflegends.com/en/c/skin-champion-concepts/3ixt4amr-whyyyyyy-riot-why-why-change-urgot-that-much?comment=0021).

ANYWAY, tl;dr: The Champ that Ekko is fighting in his reveal video is most likely a new, upper tier Blitzcrank skin (Augmented Blitz?) that will be joined by some sort of expanded lore reveal/origin story for the Great Steam Golem.

Lets take a look at some evidence:

First, the physical similarities, because they're quick and easy, and then we'll get to the meatier stuff later:

[Although I noticed a few of these and had the idea on my own, originally, Mr. Tamer and Spoody helped solidify the idea for me, so I'll just summarize them]

1. Mr. Tamer: Same 3 Flat Finger design on mechanical fist. Spoody:
2. Similar body shape (top heavy and tiny legs) = similar in-game readability
3. Green circle plate/thing on stomach mimic's Blitz's Circle on his chest
4. his fist lights up when he goes for knock up punch (similar to Blitz's E)
5. Vials on his back mimic Blitz's exhaust
6. techmaturgical fist uses a ton of bolts in tubes in construction
7. he uses only his techmaturgical fist to attack
8. it seems he has some sort of ability to charge up and move faster (Blitz's W).

In the video: Just before Ekko rewinds time for the first time, we see this Zaun character's fist approaching him much more quickly than the rest of his body, which could be a possible hint at a rocket grab. Also, if you pause the frame right before time rewinds, you get an image over Ekko's shoulder that's very similar to the one in Blitz's current base skin, with the exception being that the hand is curled into a fist, rather than spread out to grab him. However, his rocket grab is represented as a closed fist in-game, rather than an open hand, so this still fits the Blitzcrank model. -Also, if you freeze frame at the very end of the fight scene, as Ekko is dodging his punch (Power Fist, by the way), we see 3 raised knuckles similar to those on Blitz's fist, and the bolt Ekko cuts off his arm is very nearly identical to the ones in Blitz's Power Fist icon.

Now lets talk about Blitz's (and Viktor's) lore, and why it totally allows for this to be a thing:

We know that, in Viktor's timeline, he first constructs/creates Blitzcrank, then has his research stolen by Professor Stanwick Pididly, who then uses it to resurrect Urgot, and then Viktor locks himself away, replacing the vast majority of his human anatomy with advanced techmaturgy but leaving his mind, integrating it into the machinery, which helps boost his learning capabilities and removes all of his emotional capacity, other than a small amount of lingering resentment for Pididly.

We know that Viktor is a genius in science and engineering, especially in techmaturgy, and no great scientist or engineer would do possibly lethal testing on a live subject (especially himself; I mean, c'mon, he's basically doing a brain transplant on himself) without some sort of prototyping or primary testing first.

So, WHAT IF Blitzcrank is Viktor's prototype for techmaturgical prosthesis. Consider the possibility that, before becoming Full Metal Alchemist: League addition, Blitzcrank was some sort of significant thug/brawler in the long line of Zaunites who have some involvement with the Noxian military. Viktor, as a student at the College of Techmaturgy, creates a prototype prosthetic arm for him, which inhances his fighting ability (Blitzcrank was originally created to be a brawler-style character, hence all the AP scaling). Then, in the fight with Ekko, something goes wrong and he is killed. In an attempt to save his test subject, Viktor rebuilds him as a Steam Golem/puts his mind into a Steam Golem, which retains the techmaturgical arm. However, he discovers that the swap completely erases all of Blitzcrank's memories (which is how he knows that integrating his own mind will erase all of his emotions). Then, he starts "exhibiting unforeseen behaviors" and starts to learn again! (which is how Viktor knows that integrating his own mind will increase his learning capacity. He regains his own sentience with a new personality (his old one having been wiped, similar to Viktor's emotions) and decides to leave on his own.

If this is true, it creates the research that PIdidly steals and uses to resurrect Urgot, as well as establishing precedent for Viktor's complete techmaturgical transformation.

Also, we get a new, awesome Blitzcrank skin!

Lastly and most importantly: Rito is in the middle of a huge lore revamp! Blitz's lore is currently very ambiguous and doesn't actually tie him to any other Champions on Summoner's Rift; his connection to Viktor is created in Viktor's lore. If this is the case, this fight, along with Ekko possibly killing his pre-Golem self, sets up a very interesting character interaction between Blitz and Ekko, as well as giving him possible ties to Urgot, Singed, Warwick, and other Zaunite/Noxian Characters who may have known Blitzcrank in his pre-Golem life.