HP, yes, that is a very useful feature of OCIO, but it does have some limitations worth noting. First, the inverse Lut1D evaluator is too slow for realtime processing, so in Autodesk apps we convert it to a half-domain forward LUT (similar to your second point). The other limitation of the technique is that the shaper must be uniformly spaced in one of the two directions. So it is not possible to losslessly represent an arbitrary IndexMap using that technique.
Because of this, when OCIO reads a .csp transform it resamples the shaper (“prelut”) into a 65536 entry forward Lut1D. Unfortunately it is a uniformly spaced (i.e., not half-domain) LUT and therefore may lose accuracy (for the same reasons as Nick illustrated in a recent post).
Doug