Re: Optimal halyard length?
Another vote for simply switching to rope that will pass over the sheaves you've got (unless you've got reason to believe there's a problem with them otherwise). You could make them long enough to run back eventually, though that will leave a bigger coil at the mast in the meantime.
If your reef lines are at the mast/gooseneck area then there's not a lot of point in running the halyard back, esp if you sail alone much of the time.. So to make leading aft effective you'll be best to lead the reefs and the halyard aft at the same time. If you do have at least one helpful crew then you can work around having the halyard in the cockpit and the reef lines at the mast, esp if you have some sort of self steering to help as well.
The fact that the wire makes it to the winch itself is more about being bad news for the winch drum than anything else.. you can cut the wire short, recrimp the eye and shackle as long as the rope tail is still long enough to reach.. but I'd get rid of the rope/wire combos in any case.. no need nowadays, and you'll avoid bleeding from jaggers now and then.
With all rope halyards, you can forego any sort of shackle and tie the halyard on, with extra length you can shorten it many times in the event of chafe - and no heavy shackle to smack you upside the head if it gets away on you..
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)