One where the "power and flexibility" of nixpkgs is encoded in the data model?
If there is something that can be done in the nix language that can't be expressed in the underlying model that needs to be used by another frontend then it should be represented in the underlying model so another frontend can use it.
To put it another way, if you're designing a client-server model where there may be multiple client implementations you don't bake big chunks of the implementation into the clients, you provide it in the server interfaces and data types.
Okay, but... how? You can't serialize a function or a closure very easily. I'm unaware of any language which attempts to do so.
Not having functions as values (true of pretty much any serialization scheme I've ever seen) makes serialized data structures strictly less powerful than data structures in code.
> that needs to be used by another frontend
I don't think this was ever a goal of Nix. But if it was, well, you would end up with something considerably less powerful for the reasons I stated.
