New house environment control

It has been suggested I post here, thanks in advance for any input.
I have a 6 month old bungalow in Ottawa, Canada. It is equipped with a forced air Bryant model 340MAV natural gas furnace, a Bryant 593C a/c and a Venmar model 4100 ventilator.
I like to run the circulation fan on low speed continually, especially in the summer and winter. The furnace controller does not provide for a third speed to be selected controlled by the thermostat on-auto fan switch even though the fan motor is 4 speed. Does any one see any major hazards in adding a double throw, 3 pole relay to allow running the fan at a low speed when selected at the thermostat and enabling the two highest speeds for a/c and heat when there is call for temperature change.
The Venmar ventilator is installed with a humidistat for control. I don't think much of this because in the winter when all is closed up and the humidity is low it never comes on, just when you would like some fresh air. I propose to control this by a programmable timer switch. Any thoughts? Additionally it collects air from ceiling level on the main floor and dumps fresh cold into the basement, my shop area. What if I connect the fresh cold into the furnace cold air plenum and wire the furnace fan to run at low speed whenever the ventilator is on. More thoughts?
Perhaps there is a much better scenario than this that will not cost an arm and a leg.
Comments and suggestions (serious) please.
Thanks, John.

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