Regarding your wiring design I would need to see a diagram in order to give you good feedback.
Basically, the mechanic I work next was telling be about this. I believe your wire coming from the accessory would stay the same. The wire that you'd normally run to your switch would be looped to the wire that's going to the battery. You then would take your ground wire and interrupt in with a switch.
So if I have my lights coming in on 87. I'll run a short wire from 86 to loop into 30 that runs to the battery. 85 will go to the switch. I think that's how he was saying.
In my opinion, I think it's just as easy to run it normally and have the hot go to the switch. I had just never heard of it being done like that and wanted to get your thoughts on it.