I couldn't second the initial post of this enough. Not so much for the loot system because I've never bothered with it much. I got enough S's on champs that I got some 50 chests for free this season so I'm content with all the free content that got me. Even on top of that I spent money directly on specific things and skins I wanted.
That bit aside.... I've heard about Riot tweaking the orange essence system because of the financial loss from Runes Reforged and the blue essence changes and I agree that they most certainly have other options to bring in revenue that aren't taking advantage of. Announcer packs being a huge one. If I'm correct (and correct me if I'm not) there is one game, I think HoTS, but I could be wrong, that has already been offering announcer packs with success. Every event Riot has done where they've given a different announcer for said event there has always been praise for it and some part of the playerbase who thoroughly enjoyed it. It's very reasonable that if Riot offered the Gangplank event announcer, Project announcer, Thresh announcer, Star Guardian Ahri announcer, to be permanently on/accessible via purchasing an announcer pack a significant amount of players would readily buy one or more those just as much as any skin they like. I know I would. I'd buy that Star Guardian Ahri announcer pack in a heartbeat even if the thing cost me as much as an Ultimate skin.
Map skins are another great option. I've seen some players do this anyways through third party programs and services. That's potential free money Riot has passed up for seemingly no reason. There's so many more cosmetic options open to them to find new paths of revenue than just strictly skins. Emotes, while I believe they should be slightly cheaper than they are, was a nice branch out in my opinion. I'd like to see Riot recognize they can branch out even further.