Maybe the key to a good universal LLM is having multiple fine tuned models for various domains. The user thinks he's querying a single model but really there's some mechanism that selecting the best model for his query out of say like 300 different possibilities.

This also helps distributes traffic as a side effect.

I guess the problem is how the conversation would flow. If the user changes topics from say art to quantum physics then asks a question about quantum physics and art then I'm not sure what the algorithm should do.