Well, I think there is some information you are missing.Sponsored Links
When a PKG is installed to the PS3 (among other things) it extracts all its files to a special directory. In those files is the PARAM.SFO.
So then, one can get the file from the directory (mind you, the PKG is gone, it has already been extracted), edit it, and replace it.
The problem is, you can't do this on a retail system anymore. Possibly with 1-2 games, that use online update features , that you can edit files passed to it. Games like Resistance, Warhawk and a few others worked this way, alas most do not any more.
And yes, one could in theory use any PARAM.SFO, but you should not. The SFO includes other details in regards to Audio/Video resolutions, game type (save, executable, patch), remote play etc.