If the problem is caused by feedback control, and/or microphone dynamic range, and/or processing limitations, perhaps the real root of the problem is the size of the aids.
The microphone is close to the speaker, so feedback is inevitable. The microphone is tiny, and I’m under the impression that dynamic range isn’t such a problem with bigger mics. (Can anyone confirm?) The electronics are tiny, as is the battery, so processing options are limited. Perhaps this is why people report better results with headphones - no feedback to control.
So one solution would be to use a larger device with its own microphones, either connected wirelessly to the aids, or with headphones. Normally we want our aids to be inconspicuous, but in some situations, eg in an auditorium, bigger might be acceptable. Do such devices exist?