I use leadcore line to fish for cutthroat in lake Wa. I suppose it would get you down to any depth you desired. it comes in 12 to 40Lb test. the only draw back would be the nail knot in the end where you tie on the mono.
you can reach great depth with a fair amount of speed but you have to let out a mile of line to get down. good idea though. I was thinking of rigging a magnum hot n tot with an oversized bill and trying that out in the lake to see if it would work. That way I could still use mono or fireline. Good Luck!!!