Is there a well defined ‘domain boundary’ between ModelingToolkit and JuMP?

I currently use GAMS and the Conopt solver to solve very large *square* systems of non-linear equations. I.e. exactly as many constraints as free variables. This is not strictly optimization of course, but rather seems to fit better under the ‘modeling’ umbrella. On the other hand, JuMP can obviously be used for this type of problem and the ability interface with GAMS and thus continue to use the Conopt solver is extremely valuable.

I have implemented a number of features in a GAMS pre-processor to help manage large square systems and would like to implement some similar features in Julia. Would features specific to managing square systems (for example easy mapping between endogenous variables and associated constraints) belong in JuMP (or an extension package)?