Although I agree with the rest of your post, this seems to be an exceedingly bad idea. In all of the aircraft I have flown, setting carb heat to hot also bypasses the air filter. This means that debris thrown up by the propellor, such as sand and gravel, can enter the engine without being filtered out. This can lead to all sorts of damage to valves, pistons, cylinder walls and so forth. Not good.
I realize that there are situations where taxiing without carb heat will lead to almost instant carb ice, and in that case you have no choice but to apply carb heat, or abandon the flight altogether. But to taxi with carb heat on by default, even when not required, sounds like an invitation to very costly damage.