Why not release Sewn Chaos Amumu and Blitzcrank as an event or good behavior reward?
Background: If you didn't know, Sewn Chaos Amumu and Blitzcrank were released for testing on the PBE. They were met with a lot of criticism and Riot decided to simply scrap them altogether. They already had their in-game models and splashes, they were ready to go.
These skins are not bad, not bad at all. Maybe they are inferior to other skins these champions have, have a few issues, and probably won't be that popular, but they're not bad. ESPECIALLY not bad enough to be totally scrapped when they're already made.
Why not just introduce them into the game in another way? If they aren't going to generate any profit, yet their models and splashes are already made, there's no reason to flat out cancel them. I actually like Sewn Chaos Amumu but I have Surprise Party already, so I would never buy it but it would be cool to use every now and again.
They are more than good enough to be given as a freebie as they are. You can release them in any way shape or form you wanted. Blitzcrank and Amumu are also low-cost, old champions easily accessible to new players. You could release it as a cheap, fair priced bundle, or just give these skins away to everyone so that new players especially could try out skins. It could even be an IP Bundle, being the first non-chroma skin to be purchasable with IP. The possibilities are endless and it'd be a shame to just throw these skins in the garbage.