This seems like a fundamental misunderstanding of how generative AI works. To accomplish what you're describing you'd need:

• An instance of generative AI running for each asset.
• An enclosing instance of generative AI running for each scene.
• A means for each AI instance to discard its own model and recreate exactly the same asset, tweaked in precisely the manner requested, but immediately being able to reincorporate the model for subsequent generation.
• A coordinating AI instance to keep it all working together, performing actions such as mediating asset collisions.

The whole system would need to be able to rewind to specific trouble spots, correct them, and still generate everything that comes after unchanged. We're talking orders of magnitude more complexity and difficulty.

And in the meantime, artists creating 3D assets the regular way would suddenly look a lot less expensive and a lot less difficult.

If all you have is a hammer, everything looks like a nail. Right now, generative AI is everyone's really attractive hammer. But I don't see it working here in 36 months. Or 48. Or even 60.

The first 90% is easy. The last 10% is really fucking hard.