Should AbstractBatchNLPModel be a subtype of AbstractNLPModel?

I think the batched problem can be solved as a monolithic NLP problem, and in that regard, should we make AbstractBatchNLPModel a subtype of AbstractNLPModel? For example, an `obj` can be implemented simply by
```julia
function NLPModels.obj(m::AbstractBatachNLPModel, x)

# query nx and ns from the proper place

return sum(NLPModels.obj(m, reshape(x, nx, ns)))
end
```