Based on what you described, I would definitely not recommend it, for basically all of the reasons you have already identified. 😉
As long as your bunnies are getting enough exercise inside, they really don’t need to go outside to be perfectly happy. In fact, it could be harmful and frightening to them, since you mention there are lots of predators in your area and probably diseases as well. Rabbits prey animals, and are creatures of place, so in general they feel the safest when they are in their home territory (unlike dogs, which like to go exploring). Is there a particular reason why you want to take them out?
Harnesses themselves are a very contentious topic, because if the rabbit struggles or spooks they can injure themselves and/or escape. They should only be used when the rabbit is very well trained to return to a carrier, and only used in a very safe place. So yeah, I wouldn’t do it.
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.