Routing for a blaze single coil
If you really love the sound a single coil gives you in the middle then sure its worth it. Is it worth it to me?? hell no. single coils have no place anywhere near my guitars, much less the middle position.(or the neck for that matter) But if you like it, Sure. Cost for routing? My GUESS is maybe around 40-60 dollars. Probably closer to the 40 range. My friend had a humbucker routed into his Fender and it cost him 60. But I think he got ripped off because he went to Guitar Center *(I know I know, what was he thinking...Well he already had taken it there before telling me).
As for the switch, I'm not sure about this so someone else is gonna have to help, BUT I would think it should be fine to add a single coil to, you just need to change the entire setup. I remember the RG7's have a "special" setup which was different from JEM/RG/UV's. Whatever it is now, I'm sure you could wire the switch to be 1-bridge/2-bridge single coil and middle single coil/ 3- middle single coil/ 4-neck single coil and middle single coil/ 5-neck
or you could wire it anyway you'd want. but if I ever had a h-s-h setup thats probably the wire i'd wire it.