not possible at all, considering an atari is only able to handle mere kilobytes of data, and its not got a function built in to run certain data off of a filesystem, you would have to have the cartridge forward the ROM's data to scratchspace that the atari would read off of (controlled entirely external to the atari itself), but then you would also have to consider a 2kb ROM may not run off of a 4kb scratch space just because of the mechanical way the atari pulls data off of a ROM. A solution would be to have a cart for each romsize, or a switch to physically change between scratchspace Roms pryor to initializing the forwarding.
so if you've got the know how to make an entirely external rom read/writer in that configuration, I suppose its possibly possible.