Why don't you stick with the Bowline. 1. It doesn't have a potential lethal weapon hanging on the end of a swinging pendulum if it should ever get loose. 2. You can end for end or cut off a little of the line to shift wear points greatly extending safe working life of the halyard. 3. The proper threaded halyard shackles take longer to attach than it takes to tie a bowline. In short, there's no advantage and a lot of downsides, like safety
and cost, to going with a shackle.
We've more than 10,000 miles using bowlines, instead of shackles, without a hitch. No conks on the noggin, halyards lasted for the entire cruise
, and you can tie them off anywhere.
Don't let the phu-phu people talk you into an expensive, unsafe modification to a safe, efficient arrangement.