Make use of DifferentialEquations.jl
Using the abstract solver interface as defined in DifferentialEquations.jl would make it possible to use different solvers in the future. In particular the option to use solvers written in Julia that support all Julia data types would create new possibilities.
Yes, this is already planned (mentioned at beginning of README.md file and in the "Plans for version 1.0").
Nice, but I think having an issue for it is a good place to discuss the approach and the progress. To implement this, the main place to make changes is simulate.jl. Is that correct? If the needed changes are implemented here, would it also be needed to modify Modia.jl? And which tests must be passed for the new implementation to make sure it is functional equivalent?