Since you've developed the portable app to use the archive compression power of 7za to compress ZIP and JAR archives, I'd like to suggest that this app be supported to recompress Android Application packages (.APK) as well.
I've run a test on only on app for the moment. But I cheated this way by changing the file type to ZIP and then running it through AppComactor's archive compression option. After the process, I changed it back to APK and tried opening it with the latest Android operating system (my phone and the SDK's emulator) to see that the installation was a success and the program could be run without errors.
With this possibility, I'm hoping that someday the Android application packages could be used in any future portable apps in under the same manners as Java and ZIP supported apps have.