I think what we need to do is create a .j2a "package" file, a file significantly smaller than a .j2a file (say, anywhere from 50kb to 1mb) but has everything needed to create a new .j2a file. Also, it could be based off of how "different" it is from the original .j2a file; the more sprites changed, the bigger the .j2a package file, since the package file only contains the sprites changed.