This isn't precluded under US regulations. Broadcasting means transmissions intended for the general public, as opposed to other amateurs. One way communicati

This isn't precluded under US regulations. Broadcasting means transmissions intended for the general public, as opposed to other amateurs. One way communications are generally prohibited too (except in certain cases like beacon stations and remote control), but as you note-- what you want doesn't need to be one way. It's not even uncommon on HF for people to blather on for many minutes at a time without pause. People could totally do lectures with Q&A, and I imagine many repeaters would be perfectly fine with that use.