Hey Techlord,
I’m sorry for suggesting it’s like a Pyramid Scheme, I think that was kind of unfair. Cos that’s not what it is exactly. What I was pointing to was the idea of Content Creators, buying and selling to and from each other. That’s the similarity I drew with a Pyramid Scheme.
But the problem is dude. Is that building things in this Modular way is - in my experience just not fun - for artists.
Yes modularity is a thing. But it takes vision, and creativity to make these things. Hence what you see on the Unreal Marketplace - yes there are lots of modular packs. But mostly they come in sets, which express an over all creative vision / idea of a scene or a character or some props.
Why would artists want to make assets for your store, when they can just make assets for the Unreal or Unity Marketplace, or Turbosquid or whatever.
It seems to me, your trying to combine a Game with an 3D Asset Store. While that is a novel idea… honestly… I cannot think of any reason why anyone would actually want to do that.
Either your making a Game. Or your making Assets to sell on a Storefront. But both? Hmm. I don’t know.
Personally, wouldn’t you just be better of making a Game? And ya know not trying to make an MMO on a royalty basis - cos ya know that stuff basically never works. 
And I’m not trying to discourage you. I’m just saying maybe try somin a little more realistic?
And honestly - everything I’ve learned about MMOs is that they are hard to make, and often fail. That’s what I’ve learned and I don’t wanna forget it, I wanna learn from it.
Sorry dude. Just my 10c.