DIY - Headlights off with the Ignition Switch

[townkat]

hi all,
i was just wondering, aren't the headlights already powered through a relay from factory? (or all the power go directly trough headlight switch ?)
if so can't we make the change directly there? without adding another relay? just by changing the command source?

btw i have an yaris d4d, automatic transmission, with keyless entry and start and digital dash and i love it