I think one of us is confused, but here is what AI says about Arduino RAM
You don't access the 32KB RAM on an Arduino Nano R4; instead, the Arduino IDE automatically uses the microcontroller's 32KB of RAM for variables and data, so you can simply write your sketch as usual, and the IDE will handle memory management. No specific commands are needed to "access" RAM; the microcontroller's RAM is volatile and used for dynamic data like variables, local arrays, and the call stack during program execution.
Since it's not directly accessible, your concept of making it bigger via a virtual function is not possible.
All that you have accomplished here in my humble opinion is add another layer to the SD card that accomplishes nothing of benefit I can see.
Please feel free to correct me if I have misunderstood.