"what I'd like to see is a closest to the hole-type mode with putting ONLY -- for practice."
Well, yes, exactly like a practice green.
"Practicing" putting by aiming away from the hole seems completely counter-productive to me. When you're trying to master a skill, any skill, why would you practice mistakes? In terms of getting bored, players will practice for precisely as long as it takes for them to get comfortable with a particular shot, not until the entertainment value has dropped below some arbitrary threshold.