I have 1 problem with that idea, Lead isnt good for humans, fish, anything. Think about how many lead sinkers have already infested tthe lakes we fish, its the reason tungston is #1 right now. My solution to your problem is what i do try a light braid, you will either move that rock fray your line, i have snapped braid on rocks but only from bounceign a jig in between some rocks with otu checkign my line for a hour.
see if my idea works before u use lead man!