An interesting unique mechanic.
This could be something that the player has to actively use (like a grappling hook) or something else that changes the structure (or the gameplay) of the obby massively. Or both of them mixed.
Not sure if people are willing to buy game passes for things that they would complete, and leave instantly, since there would be nothing to do in the obby.
My suggestion would be that, besides building more stages, try adding badges or in-game items to award the player for passing a certain mark in-game.
By the way, is this topic for another post you have created on showcasing an obby? If so, I might have a few ideas besides the one suggested in this reply.
Leaderboards
One way to encourage users would be to add Leaderboards to your game! They will be able to compete with players globally on who can complete a certain stage the fastest! Maybe stages which are made slightly harder for Players to complete?
Players will be able to achieve a badge if they do make it to one of the stage’s leaderboards. Of course, there would always be an issue about exploits, so maybe that should be considered first before implementing this.
Minigames
Obbies are generally very restrictive. You complete an obby and there simply isn’t anything to do there. If that’s the case, your game might be popular for a while before Players lose interest when they reach the end and there’s nothing much to do.
Therefore, Minigames are a good way to let Players interact with others. You can make it such that Players will need to pass a certain stage in order to be eligible to participate in Minigames. When a minigame starts, it’ll be sort of like TOH - randomly generated obby where a Player needs to get to the end of a given time to receive a prize.
There can be a lot you can expand from here, like win stats, credits, badges and in-game items.
These are just potential things that I feel may engage the Player.