Max, measure across the flats where you want to cut a dovetail. Subtract the bore diameter from that. Divide by 2. That gives you the barrel wall thickness.
For example, a Rice Golden Age B weight barrel measures .750” (¾”)at the thinnest point in the waist. Subtract .500” (½”) for a .50 cal. Bore. That leaves .250” (¼“, divide by 2, that leaves .125” (1/8“), that‘s the wall thickness. That leaves .025” for dovetail depth to maintain .100“. Not enough for a dovetail, in my opinion, also keeping in mind the depth of the rifling. If you have to place the dovetail at that point I would solder it on. Like Ken said thin the lug base and file a shallow relief in the barrel.
I wouldn’t move a lug just so I could dovetail it. The lugs where not located in a place on the barrels that made this a problem on the rifles I used these them in.
But, with a .45 the thinnest point in the wall of the same barrel is .152” + so a .050”dovetail will work fine anywhere on that particular barrel. That’s plenty deep enough to hold a lug.
Bruce Everhart