I don’t think I’d be interested in paying extra money on top of the original purchase just to access cosmetics (better weapons, fancy clothes, new spells) that don’t enrich the preexisting narrative beyond just looking good or making things easier.
An expansion pack with an exclusive story of its own however, even if shorter than the main plot, would be quite interesting. The best video game example would be the Witcher 3 expansions - Hearts of Stone and Blood and Wine, which offer both individual story and upgrades to the player.
But could IF games implement a similar expansion? A short and sweet extra storyline with exclusive characters and quests that expand its parent’s world building scope, perhaps showing new perspectives and cultures that couldn’t be featured in the main plot?
It should be differentiated from a pay wall that restricts full story content unless extra is paid, rather it would need to be a legitimate expansion or companion piece that the main game can function optimally without yet maintain an incentive for fans of the game to buy it.
For e.g a Heroes Rise expansion pack where you play one of the supporting characters, say Black Magic during their early years and rise to fame or Rebellion’s story or a Prodigal POV set during the Hero Project where she learns the truth about her mother, leading up to the events of Herofall.