It depends on how stock you want to keep it looking. I already had POs holes in dash so I mounted a push button. You could hide a push toggle under the dash your seat anywhere. You don't need a relay to the starter as the starter solenoide is in effect a relay itself. Caveat to that is a remote starter that functions when the ign switch is in the acc. On position, means tbere will already be a load on the battery from accessories if they are on while the engine is being cranked.
This not really a problem with a good battery and charging system, I've done it for years. The voltage drop might be hard on a high end amp if you have one in there, big amps are not my thing though just spitballing that one.
Finally I eventually just bought an aftermarket ign switch that does everything I want it to and doesn't break keys. I also have electronic ign so I'm not stock, just practical classic.