There may be several topics in that thread.
- color space
- accuracy
- compression
Color space
If you use a hadclut built for sRGB I think you could try to convert the file (which is an image) to Adobe RGB to get a new hadclut working in Adobe RGB. That should work. Am I wrong ?
Accuracy
I’m afraid you cannot increase the level of information contained in the LUT.
The precision depends on the size of cube and of the numbers themselves. Most of the halcluts are 8 bits but some of them are 16 bits.
However any transformation of the cube at constant size will tend to decrease the accuracy.
Compression
Some time ago GMIC used to provide routines to compress / uncompress LUTs.
You’ll find some tips here but I don’t know if that still works.
I hope that helps