P: Adding a 12 and/or 14-bits/component option in JXL (JPEG XL) export settings

Note that LR's export of JXL is currently broken -- it produces files that are much too large:

https://community.adobe.com/t5/lightroom-classic-discussions/certain-raw-files-export-unusually-large-with-jpeg-xl/m-p/14896912#M381186

I think 16-bit JXLs, when correctly implemented, provide the "better compromise between quality, absence of data loss and the final size of the exported files" you're looking for.

Imagemagick's "magick" utility, which uses the "libjxl" reference library, produces reasonably sized 16-bit JXLs. For example, it converts a Canon EOS 5DS R 50 megapixel / 53 MB raw to a 16-bit, quality 90 JXL that's 8 MB.  It converts a Nikon Z 9 45 megapixel / 52 MB raw to a 16-bit, quality 90 JXL that's 4.5 MB. 

I can't figure out how to reduce the bit depth of the JXLs to 14 or 12 using "magic" (it may not be implemented), so I can't compare the file sizes with 16-bit. But it may significantly less than 25% (= 100% - 12/16), since the compression algorithms might do a good job of compressing the unused extra zero bits.