Regarding the switch, the solder connections look OK but I see no means of mechanical support for the wires. Vibration can quickly work over the wires and cause fractures. Unless you are not showing something that would add that mechanical support, I would use a different type of switch.
Regarding the overall wiring layout, yes you can do it the way you have it laid out but it can be simplified. I prefer to use an IBEC (Ignition Battery Eliminator Circuit) that powers the ignition from the receiver battery. The device I prefer is supplied by Tech Aero .......
http://www.tech-aero.net/ultra-ibec
This device provides ignition isolation and filtering, over current shutdown, voltage regulation and engine cut off via one receiver channel. These have proven to be extremely reliable and their use greatly simplifies the wiring by completely eliminating the separate ignition battery and switch. The RCexl cut off device can also be modified to eliminate the extra battery and switch but it lacks the regulation, current control and isolation the Tech Aero offers. Both devices are in wide spread service.
I'll let others debate the separation of ignition / radio components in the aircraft but my experience has shown there are few if any problems if good installation practices are followed. This is one of those areas where we each do our own research and do what we think will be reliable in the long run.