IMO, Probably the best option would be to weld in pieces which have a sliding top gate. So that they can be "opened & closed", much as is an anchor
shackle. Only in this case, they'd obviously have a much wider opening, & space for more heavy line(s) than does a standard shackle.
But if you configure them this way, & so that the "shackle pins" both; stay locked open, when opened; as well as locked shut, when closed. All of this, sans tools; in both instances.
And so that the "gate pins" are configured so that they're out of the way, & cannot accidentally get bent when the fair leads ("shackles") are open. Then you pretty much get the best of both worlds.
Basically something which looks & functions much like this WINDLINE LOCKING LINE CHOCK Windline LC1 Sailboat Supplies, Engine Parts and Boat Parts
But with a bit more room inside of it when closed, so as to accomadate multiple large diameter lines, when wrapped with heavy chafing gear
And they need to be designed so that the pin both locks open & closed, as well as being protected from bending/damage, as described above.
Although if you want a KISS solution, you could just have some large, stainless steel
, Wichard shackles with captive, self-locking pins welded into those locations. Perhaps even having 2 such shackles welded into each opening, with small gussets welded into the spaces in between them, to fill up the space. And to more firmly secure things in place.
However, a Crosby shackle, with a threaded cross pin, with a hole for a safety
wire in it's end, might be even better. But it'd be a bit more abrasive on lines, due to it's galvanized finish. Vs. the slick, polished surfaces of a stainless shackle.
I'm speaking of ones akin to these http://www.thecrosbygroup.com/catalo...or-shackles-4/
That said, I'm sure that you could have someone make up a hybrid of the two shackle types. Having the best features of both. And that used a common sized stainless bolt for it's cross pin. After drilling it's end for a ring, or split pin, of course. Plus drilling a hole for a retention, safety
wire into the bolt's head
. So that it can't accidentally go swimming.
Also, there are bolts specifically made to function as locking cross pins. In that they have a small slot cut into their tips, which house pivoting, rectangular metal cross pieces. Who's function is to keep the cross pin from accidentally opening up.
But sadly, I don't know the correct terminology for such an item, or who might make them. Perhaps another CF member