I would and a Diamond shape to the list.
The system (and presumably the coding) is already in place to add such a simple bit of functionality. Why not have it function like the Drawing Border tool, where you have a file within the library and can choose from a group of symbols. If you want to change the symbols for the way you work, you just add a symbol to the file and get working.
While I am on a roll, I hate the default electrical symbols tool. Why can't I change the way those symbols show up? I understand proprietary information and all that, but really, being able to customize these things seems like such a simple thing. And something that almost everyone who uses the program is surely going to want to do at some point.
Just my two cents.