The size of the head doesn't do much at all to help someone hit further, it just makes the head more forgiving to off-center hits. A lot of Tour pros don't even use a head as large as is allowed. I am no Tour pro and my driver isn't even the max of 460cc. The smaller profile at times can actually be hit further because it cuts through the air quicker. Limiting the head size hurts the average golfer much more than the Tour pro.
Also, square grooves help out of the rough, not the bunkers. The type and density of the sand has more to do with the spin out of a bunker than the grooves. Your point about it is still valid, because that only applies to the pros and club manufacturers (for now).
Now you know why I play disc golf instead of normal golf. My clubs get used about 3 times a year on an actual course.
In any case, just because outlawing jump putting would make it harder to approach doesn't mean we shouldn't do it. And those who say we might as well go back to lids and tone poles are completely missing the point. Just as the PDGA can restrict technology (or even push tech backwards) to make the game more fair consistent, disc golf can and should do the same thing. Jump putting is detrimental to the sport because it is impossible to call fairly, and in my opinion additionally detrimental because it has absolutely zero decorum.