Riot games tried exactly this with Riot Forge, but it was shut down because none of its 5+ games they tried amounted to much in terms of sales.
Seems like a generic platformer priced at €30, but don't worry! You can also buy skins for a couple extra €.
--
Looking at another one: https://store.steampowered.com/app/2252143/The_Mageseeker_A_...
An action RPG where you can buy extra spells for your character as a DLC...
--
Hmm, no idea how their business model didn't work out.
If that's true, there may not have been many at Riot who were super passionate about it. Obviously Ghostcrawler was but was probably spread very thin.