Is it permissible to add other icc profiles to this package?
Personally I wouldn't. I would keep 3rd party profiles in the standard location. If you load them into this package and then ever need to reinstall the driver, you will have to do it again.
To me it is annoying that Epson chooses to do this. I wish their installer would just place the profiles in the standard OS X ColorSync Library - and even give you the option of which ones you want to install.
I have opened up the package and deleted profiles I know I will never use, which can make navigating the choices easier when in photoshop. Of course, I have to do this every time I reinstall the driver. It would be nice if the system and the applications worked together to make this easier. LR is a step in the right direction ... at least I can control what profiles appear in my popup so I can have a fairly nice concise list (and don't get 50 that have nothing to do with printing).
To me ColorSync utility is pathetically designed ... not much use as a utility. I open it and I get hundreds of profiles left over from the past several years. Seems one of the purposes of a "utility" is managing things like this but you can't delete them nor navigate to them from this utility. Come on Apple ... do what your famous for and make the software logical and functional.