The game DOES have a storyline, REGARDLESS of whether or not YOU PERSONALLY like to read it. Some of us do give half a **** about lore, and just because YOU want to be OMGLOLSNIPZ doesn't mean you have to ruin the setting for the significant portion who DO care. Go play Kog'maw if you want to be a sniper, he fits the playstyle, just not the aesthetic you stereotype a sniper as.

As has been said, there are no futuristic champions in the game right now. There may be futuristic skins, but thats it. Steampunk =/= futuristic. Blitzcrank is put together with magic as much as with technology.

They could just say a space marine was warped in like Nasus was warped from a dimension with an Egypt-esque region. BAM, lore problem solved.

Add Space Marine General
He was fighting a great war in his world
Was warped during a summoning mishap (these seem to happen all the time!)/A wizard did it (such great story telling!)
Space Marine decided to fight for the Institute of War to bring his world's brand of violence to Runeterra
He fit right in

The end. U jelly?