This package defines new struct and implement the MOI API for them. We still haven't released this package because we know there are many more combination to add and we don't want to maintain all these and make them efficient.
We've made the effort to make MatrixOfConstraints efficient and we make an effort for most of the solver wrapper to use MatrixOfConstraints.
So I think a better approach for this package is not to define new struct but just add simple functions that make it easy to create the right MatrixOfConstraints instance.

Note that if this MatrixOfConstraints instance exactly match the one needed by solver, we may even have an even lighter copy_to, at the moment it will probably not happen since they as for the mutable sparse matrices but the solvers could in theory relax that if at some point we find it useful. It's nice that this is in theory possible but probably not high priority.

• Allow creating model from parts MathOptInterface.jl#2902

For conic, we can do what suggested in #32 (comment).