The key with all furnace/heating/cooling automations is to start at the source of heat - figure out what IT needs to do what it wants, and work from there.

They're almost always incredibly simple at the furnace/boiler - you just need to make sure that you never turn the heat on without the pump/blower or whatever is required.

My complicated Eco controller ends up with three outputs: blower on, heat on, cooling on. Three wires.