Read/write support for Bufr
The WMO's BUFR format would be useful to support both for reading data from as well as for writing data to (specially in the context of Global Cryosphere Watch). This format supported by ecCodes so this goes together with support for GRIB that has an old (half broken) implementation in MeteoIO.
More details about the format: https://community.wmo.int/en/activity-areas/wis/latest-version.