Light switch relay

I'm going to be installing a new fuse block. I'm cheap, but classy, and the fuse block I picked up is not oem style. It's has a (+) bus, with the separate circuits branching off. This creates a problem with keyed hot vs constant hot. Easy enough to use relays for keyed hot and use original trigger source to close the relays. That won't work with the dimmer function.

What I'm thinking is to put in a relay to the light switch, triggered off of a keyed source. Key off, no lights. Extra points for not leaving my lights on and killing the battery. The accessory lights line will no longer have a dedicated fuse. Instead, it will be the entire light switch that's fused. My question is, is there any reason for this to be a bad idea? The headlights will be on their own relays under the hood, so minimal power draw through the switch lines.

This will be the new fuse block: Summit Racing® Fuse Blocks SUM-900357