I re-did all my halyards this spring and kept the shackles, as I never thought of it, any other way. I do know on my main the aluminum pieces on the top of my mailsail would probably cut the halyard up, but they could be worked with a file to be smooth.
But what do you really save here? On my 20 ft. boat......my shackles weigh nothing. They are tied with a bowline knot, and don't keep the sail from hitting the top of the mast....
At least I don't think they do..................?
I'll have to check the next time I hoist the main.
There's always a different way to do the same thing...keeps you thinking.
Best of luck