Yes you can do that.I think that means that Rg will be out of the hybrid equivalent model, right?
And as the source of the MOSFETs are supposed to be grounded according to the generic hybrid equivalent model, we will have a virtual ground at both MOSFETs sources, making Rs also out of the circuit, no?
But why you simply not solve this circuit directly. Using whatever analysis methods are at your disposal to do this.