Use a 2 gang box and you will be fine.
Since you can use a deeper box, this may be the only way to go.
You can then use a blank and a switch 2 gang plate.
The switch or receptacle counts as 2 for the size wire you are using.
So a 3 way switch with #12 will count as 2 wires.
Since you can use a deeper box, this may be the only way to go.
You can then use a blank and a switch 2 gang plate.
The switch or receptacle counts as 2 for the size wire you are using.
So a 3 way switch with #12 will count as 2 wires.