With Scilab/Xcos we have the same development perspective than "The MathWorks" with Matlab/Simulink. So it may be possible to import any Simulink diagram on Xcos.
The development may follow 3 steps :
- Parse the MDL file and reconstruct an equivalent diagram.
- Implement some compatibility patterns for evaluation functions and block representations.
- Validate the approach by evaluating diagrams compatibility.
During the 2 step, you may find that Xcos lack some evaluation functions and you may be able to implement part of them.