I tried full FS access by patching an old version of CustomPFD to see if i could replace extras&info directly from phone memory.
I think some directories are hidden so i could not find the directory where the apps use to be installed.
However, i found a directory with the OEM apps (touch, extra&info, etc), but it seems that it's there only to be applied after a hard reset or something like that, so just replacing files wasn't enough. Extras&Info wasn't the only app with Interop Caps, but almost any app that is under settings has that cap.
So i unistalled touch settings and downloaded it from SD then i used MetroCommander to replace the SD files the old way (before CustomWPSystem was created, lol). Got nothing but an endless "Loading..." screen, but i guess i did something wrong.
But technically (someone correct me if i'm wrong) we can do Interop+Caps unlock using some other app from settings, right?
I'm pretty sure i've seen a settings app with a lot of capabilities in the manifest, not just InteropCapabilities, i don't remember exactly but it had something to do with SMS