like MoE with a billion "experts".

That seems promising to me too, although, the thing I've always read is that you can't make the "experts" too narrow. Even if you had a "coding expert" it has to know a lot more than coding - if you tell it to make an online store it needs to parse your language, understand the internet, what a "store" is in this context, etc.

I am not a primary source, probably not even a secondary or tertiary source, so take this with all the grains of salt.