Crazy idea or not? I believe it would be possible:
- to extend libtiff / GDAL to support JPEG2000-in-TIFF
- reprocess L1C Sentinel2 JPEG2000 files, which use JPEG2000 tiling, into cloud friendly tiled GeoTIFF with JPEG2000 compression, in an extremely fast way (not involving JPEG2000 Tier1), and with resulting GeoTIFF files being the same size & quality of the original JPEG2000 files, but with a proper index. Such a shame that the Sentinel2 tool chain doesn't generate TLM markers!