Well, it's over a year later, so I'm not sure if you built it Dropabeet.
If not, the way you'd want to do this is to wire your controller for 240V power, and add a contactor/mechanical relay that allows current to "come in" on L1 and to complete the circuit on neutral when switched to 120V mode, but current will "come in" on L1 and to complete the circuit on L2 when switched to 240V mode. So you've effectively got a dual-voltage controller.
As far as plugs go, the box should be set up for a standard 240V male plug, but make a pigtail that has a 240V female end and a 120V male plug for when you're using it in 120V mode.