I can only speak for 0.7.10 as I haven't installed 0.8. If the menu is done in python in 0.8 then I'd think the same thing could be done if you see "import subprocess" toward the top of the python script (or you'd have to add that import).

If you modify /home/pi/pimame_files/menu.py with leafpad, add the following line (I added it above the line: Menu = "menu"):

os.system("advmenu")

If you want to start other emulators, scroll down and see what command are issued to start the other emulators. If you look at the Playstation 1 menu item you will see the command '/home/pi/emulators/pcsx_rearmed/pcsx'. Just swap out advmenu with it and it will start the PS1 emulator instead of AdvancedMAME.

Hope this helps.