I have an android ROM that I can flash onto the phone using a tool like smart phone flash tools, but what I want to be able to do is to modify the system image to add APKs in the system/app directory and then repack and flash the ROM. I want these newly added APKs to behave as part of the system.
I have looked at a couple of tutorials for unpacking and repacking it, but once I repack it, it becomes unusable. Is this the correct approach or am I missing something? I'm not sure what I could be doing wrong.