Soft Halyard or Line Shackle

[Brion Toss]

Hi there,
I like this variation on the theme, and would suggest that the way is open, with this and with normal soft shackles, for an even stronger attachment, through the use of four-strand buttons or lanyard knots. That way the shackle would not be the limiting factor, and in your case you'd have deeper redundancy for the permanently-affixed piece.
My favorite sheet configuration remains a 1-piece pair, secured to the clew with a soft shackle, with the whole works coming off for sail or rope maintenance or stowage. With this, one is not limited to HM sheets.
Fair leads,
Brion Toss