combining mmxprs and/or nlsolv with mmquad or mmnl

Yes I can confirm that the appropriate solver algorithm will always be selected based on the nature of the problem. Whether nlctr objects are used in the modelling has no effect on this. If the problem is purely linear it will be solved using primal/dual simplex or interior point, depending on the Optimizer settings. If the problem has quadratic objective only it will be solved by quadratic simplex or interior point, and if the problem contains quadratic constraints it will be solved by interior point.

We do not have plans to provide an overloaded exportprob function, since the same functionality is provided by the loadprob/writeprob functions in mmxprs. These functions can be used in the case you are describing, where you use mmnl and all nlctr objects are linear or quadratic.