Exactly ^^, or I use script to check special roms and change command line.
It s totally possible with this method. But For me I think it s more ergonomic to have the possibility to use an alternative run command (just by pressing a second button during the selection) than having a system just for somes roms that need this command.
It will be usefull for exotics roms that doesn't works in all emulator (use an alternative emulator).
Some roms need additionnal parameter in command line (like for rotate screen).
Somes emulators need differents parameters for configuration eg If I want to use 2 joysticks or 1 Joystick + 1 mouse.
I just need a command line totally customable, where I can choose all I want, application and parameters (and without using integrated scripts possibilities).
It will be usefull for power-user and totally invisible for other.
In reality, ATM I m working on Amiga WHDload system, and all roms works with additionnal params
CUSTOM1 CUSTOM2 etc .... To active cheat, second button, or correct bug compatibilities, theses commands changes every time and I have more than 2500 roms, I can't use script to check all roms, will be easier for me to have:
1 - normal load without bugs.
2 - special load with special command that can crash game.
And I have already exactly the sames games in many system, Amiga ADF, Amiga WHD, Amiga HDF, Amiga CD32, ect ... with this option I can merge systems.