In Axe, you basically can't. There's a reason the Y₁-Y₀ "file" system exists, after all. Why would you be trying to avoid them?

Also, if you are going to use them, note that you can read and copy from pointers to archived data, but nothing else. For instance, you can't directly draw a sprite because the sprite drawing routine doesn't "know" how to read archived data, which isn't nearly as straightforward to read as data in RAM. And you can't write to a pointer to archived data simply because that's a limitation of the hardware. Writes to flash memory have to be done in a very special manner which is far too expensive and complicated to do arbitrarily.

I guess that does make it a bit trickier. But it would still definitely be harder to implement custom archived data reading code than to just finagle the archived data pointer into a Y₁-Y₀ file pointer. It's a bit redundant, but I'd suggest simply reading the variable's name and using the archived file variant of GetCalc() on it. That has all the code needed to convert the page and pointer in the VAT into a file pointer that Axe understands, which isn't exactly a simple conversion to make.