There are an infinite number of integers. You can start at 10 and count up forever, never running out of integers. But no matter how high you count, you’ll never count to “orange” - “orange” is not contained in the sequence of infinite integers.
You’ll need to first prove that every sequence of integers is contained somewhere in pi, since the number of possible integer sequences grows faster than the “space” for sequences in pi. In other words, I can always pick a digit that creates a valid, non repeating, integer sequence from the pool of possible sequences while never creating the integer sequence “123456789123456789123456789.” You’d need to prove that pi doesn’t do this.
Even if pi does contain every sequence of integers and you could map that to bytes which, in turn, maps to a file, this would not compress.
Your metadata directory would be larger than the raw files unless you get very lucky and your file is very early in the sequence of pi.
A byte can represent 256 unique values. 256 unique values can not compress to less than a byte. So if your index is a digit of pi where your file starts, your file starts after some other number of files. Your index is going to be the index inside of the address space of “all possible files.” This will get large very quickly.