Having the heater on hot when starting the engine provides a bypass but will not turn off by itself.
The spacer will not work because it does not have a shut off. If plumbed as suggested, the bypass circuit will be open all of the time.
The 1/8" hole in the thermostat flange will allow trapped air to escape when filling but will not provide enough flow to create an effective bypass circuit. Plus it undermines the integrity of the thermostat (not much) because it always allows coolant to flow past the thermostat, open or closed. If releasing trapped air is a feature wanted in a thermostat, buying one with a jiggle pin is a better alternative.
