there are almost no recipes for siltstone or mahogany to be useful (A mid rank tool and weapon is not exactly in huge demands of +3's) so an exclusive +3 version I would say no I do not think this as exclusive I call exclusive the entire item is exclusive, right down to the base item.
As I mentioned what is exclusive will be the materia catalyst which will be DoL exclusive. I have no idea how broad or rare they will be so will reserve judgement until I gather some.