Raw device on PostgreSQL

Hey,

for an university project I'm currently doing some research on
PostgreSQL. I was wondering if hypothetically it would be possible to
implement a raw device system to PostgreSQL. I know that the
disadvantages would probably be higher than the advantages compared to
working with the file system. Just hypothetically: Would it be possible
to change the source code of PostgreSQL so a raw device system could be
implemented, or would that cause a chain reaction so that basically one
would have to rewrite almost the entire code, because too many elements
of PostgreSQL rely on the file system?

Best regards