Problem passing index to GetSet function

When I define a Simulink.Signal with dimension >1 and set it's storage class to GetSet it will generate a C function call like this:

 get_MyChar( MyIndex )

Problem is when I define that same signal as a struct. It will then generate the C function call as:

 get_MyStruct()[MyIndex]

My problem is that I need that signal to resolve to a call that receives the index, just like the first example was doing when I define the signal type as uint8.

Any clue on what's going on, plus how can I generate the call as my application requires, without needing to resort to manual matlab code, like coder.ceval for example?

I attached a sample model where I implement what I just described. Thanks!