I'm interested in taking the "best" overall route in terms of effort & likelihood of success.
I threw in the JB Weld as a conversation piece, have no desire to use it. Actually quite surprised at the lack of horrified response.
Don't even have any.
As far as brazing goes, the buddy used to teach welding at a college & has a well-equipped machine shop.
Blacksmith experience.
Degree in automotive engineering.
Used to run his own repair shop.
Very very good with conceptualizing & hands-on improvisation in a wide area of metalwork.
Also has an anvil.
I'm not taking anything you say lightly & do appreciate your comments.
My sample has a much better blade condition than yours did.
Unfortunately, whoever fitted the guard to the sword did a very poor job.
There's a notable gap on both sides up front between the blade & the guard material in that slot.
Marked rotation of the guard, not just a minor bit of play.
Really quite loose. It rattles.
Using wood spacers on both sides of the back end of the guard would remove most of the movement, but still leave some play in the front.
In thinking through the various methods, I see a risk in material displacement of deforming the curve around the slot. It'd take quite a bit of impact over a relatively wide area there to tighten up that slot gap.
In building up solder & removing excess material, have a concern about the softness of the solder as a mass in bearing against steel.
Probably not an issue, if the sword never gets itself into battle, but...
Also, with the broadly cupped guard, not easy to remove excess material on the inside "flat" of the guard, to allow the handle to fit flush against it again.
Dremel with the right head & much care, I suppose.
I don't have a Dremel, the buddy might.
Brazing would build up a stronger bearing surface against the blade, but would be harder (literally & figuratively) to remove excess material.
Again, Dremel, I'd think, on the flats. Files inside the notch would not be much of a problem.
The buddy should be able to do precise enough work on it, but there's also the risk of heat warping on the guard.
My thoughts on the small disk are that it could be rough-cut out of sheet steel, rough-ground to shape, drilled center to provide a starting point for the slot, filed in the slot to fit tight on the blade, filed to final contour on the outside edge, and soldered around its edges onto the guard.
Smaller flat part should be much easier to do the work on than the bigger multi-curved guard.
No soft solder bearing on steel.
No danger of heat warpage on the guard.
If I go that route, I can do most of it myself, except for the soldering.
If I go the welding route, I'll have the buddy do it.
A different alternative would even be to have my gunsmith work on it.
No doubt whatever about the skills & equipment there.
I know my limitations.
I want it done right.
I have not contacted Albion or Windlass.
This'll be a slow project, has not fully rotated around yet.
Still in Contemplation Phase.
I may just go with the first 8 inches or so on the edge, as suggested, after all.
If I do, I can handle that much myself.
Denis