To stay under the Part 103 weight requirements you are almost certain to need a small, air cooled, two stroke engine. Even the best of these fall FAR short of both the TBO and reported MTBF numbers. As an example, offhand the Rotax 582s were a 200hr TBO and were known for cutting out in flight if abused or not maintained very well.
As for them being less lethal, that comes down to the listed operating areas and the limits imposed by the construction of them. In reality they are just less lethal to non-involved bystanders; they will still kill their pilots quite easily.
As for them being less lethal, that comes down to the listed operating areas and the limits imposed by the construction of them. In reality they are just less lethal to non-involved bystanders; they will still kill their pilots quite easily.