External defined variables as single input instead of many

Hello! I have many variables defined in external C code (let's say in the order 10s), and I like to modify read/write their values in the MATLAB generated code (through the developed models).

What is my best option if I do not want to have 10s of input ports in my top-level model, and I'd like to modify these external variables without allocating any further memory. (so modify them by reference)

What I tried:

-Bus object (cannot work, variables are not in a struct)

Do I have to use Data Store Read/Write blocks for example coupled with Simulink.Signal objects (which have ImportedExtern storage class)? This way I'd give up the clean input->output dataflow, and interfaces in the top-level object. Isn't there a cleaner option for this?