I think there are two things here:
Pay 2 Win Mechanics
It’s a weighty document, but I think the Minecraft monetization guidelines are a pretty good place to start, as they’re pretty comprehensive:
In their own words:
The focus is on ensuring that whatever servers sell to people, it’s not a thing designed to give someone a competitive gameplay advantage or make another player’s experience worse. It also provides a clear definition for what we consider a competitive gameplay advantage… [also] allowing the sale of effects that influence everyone in the same way and barring the sale of items that affect gameplay.
So, for example, in Minecraft:
- No purchasing more attack power, or better quality equipment
- No purchasing more lives
However, it would allow purchasing buffs that affect all players in the lobby, just as long as it doesn’t give a gameplay advantage, such as a gold or EXP increase.
Minecraft is also a good example because these rules apply to not just Minecraft specific gameplay elements, but also elements added on top of the game (like new gamemodes). VRChat is a lot more flexible than Minecraft, but I think wording this around the same exact “no competitive advantage in a V.S.” game should be the focus.
Moderation of this will require discretion, and I know that would require legalese I’m not equipped to suggest, so I’d defer to your legal team. But the focus should be - in game worlds, with a competitive focus, no purchases should be advertised as something which could be reasonably construed as a gameplay advantage.
Infinite MTX
Honestly, this one is kind of just, don’t give access to tools that allow world creators to put in infinite “click this button to pay $1.00, as many times as you want!” buttons. This leads to, often, gacha mechanics. If provided, worlds would easily fall into lootcrate/gatcha mechanics as seen in most games today.
If there is a legitimate purpose you can think of for this button to exist, I would actually like to hear it, because I’m not confident I’m accounting for everything. If there is, though, perhaps targeting gambling mechanics, and not allowing creators to put in pay 4 roll systems.
Note I’m not against IAPs, you make great points about how one-time payments could be useful. But if there is no limit to how many times a purchase can be made, I can’t see a situation such a button could be used where it wouldn’t be predatory.