Rebuild & improve Collins 516f-2

I'm rebuilding a collins power supply, and I'm thinking I should add some improvements, such as separate 6.3v and low voltage switching. I'm also building this for 240v use.

I've looked at the schematic and I can't see any reason why I can't use a low voltage say 12v across pins 5 & 7 on the power plug and use this to drive a relay to turn on the mains power, this would save the switch and avoid having to use an expensive relay with a 240v coil. It also means I won't have to change the relay if I move to a 115v area.

Is there something I am missing ? Power on pin 7 does go to pin 6 but I have not found a use for pin 6 so it actually goes nowhere !

Any advice appreciated.

Dave