My guess would have been that every tenant gets their own “handler/driver” model that updates its weights based on the user intent, problem etc.. but it has “experts” to call on demand that are pre-trained set weights. I thought this is how MOE models worked. Then a user gets access to large weights where it matters..

I don't work for anthropic, so I don't know how they've implemented their MOE... But at least with the ones I know you cannot easily "attach" another expert to the model like that. Maybe they do have a special sauce that let's them do so. If so, it may be viable but it's effect would be a lot less effective then the full version this discussion was started on.