Yeah, that's how good lighting harness is made. In the end, the total cost difference is maybe $25, a negligible amount when you've dumped $200-500 on a set of lights. For the lighting example above, you could even add a DPST switch if you wanted which gives each side it's own independent set of switch contacts housed in a single switch. I've seen a lot of switches break over the years, usually the internal mechanism that opens and closes the circuit wears out or has a buildup of burn residue from years of use. using a dpst instead of a spst switch is only a few bucks. It's one less single-point of failure, if you don't see the difference. all fuses are inline, i'm not sure what you mean there. Some people get a little fancy and buy power distribution blocks to centralize the fuses/relays/breakers, if that's what you mean. Another popular way to get power to the 85 is to get one of those fuse taps that you stick into your existing fuse block but it's an still inline fuse. The low amp fuse is there to protect the coil in relay, not the switch. Yeah, you should always try to avoid bringing high current inside except where there isn't much choice such as big stereos, power inverters, etc. All of those will have heavy wiring and big fat connectors when properly installed. The problem is you don't want to be in a situation where you've created an unknown hot spot which can be any number of things including a cheap/broken switch, bad terminal crimp, loose connection, scraped a wired going through the firewall, used inadequate wiring guage, etc. ah, all my page breaks were removed and it's all one paragraph. oh well.