This problem can only be resolved through sane configurations appropriate for shortwave, i.e. MSCs of 16 QAM, and the xHE-AAC codec
This is the only short term stopgap solutions to the HF broadcast problem.
Actually the main complaint I have against DRM is that the codec (AAC+/xHE) remains proprietary product. This not only put a hurdle on wider adoption of modern broadcast standard, it also discourage any attempt to improve or it co-opted to better systems. And indeed there is a far better solution to this kludge: why let the broadcaster to dictate the configuration of transmission signals (64/16QAM, bitrate, AAC/xHE etc.) at TX side, why NOT let the receiver to decide that at RX side depending on the local SNR level? This strategy incorporate the agility of analogue system and efficiency of digital system and DX friendly.