Great project ! How are you going to wire it ? ie how is the link used in stage 3 not going to effect stage 1.
The easiest way I see it involves lots of relays I'm curious about how your going to do it .
About the 3 stage switch if you have it on its highest/hottest setting are the other 2 (low & medium) contacts made ?

Edit: I see you don't have the switches yet