Thats a very similar idea to one I have been using for the past twelve months or so, like you I really dont like split shot, I am always afraid it will damage the line, I did think of using Olivettes, but as they only seem to do line through, I decided that I would make my own, well, sort of.
I use cut lengths of solder, which I cover in black shrink tube to dull the colour down, and fix them on the line using the green Carp tail rubbers, just like your idea, they can be altered to suit the size of weight needed, and slide up and down to wherever the weight is needed, the taper of the tail rubbers make it easy to pull out of weedy areas.
I tie on a small swivel on the end of the mailine, and attache the trace to it, or I suppose you could go the loop to loop method if you preferred.
I cut various lengths of solder, shrink tube them and take a few with me, I can always find a length that suits the float, or indeed just cut one down a little using scissors if the weight overshots the float a little.If you change the float, then its easy to change the weight without damaging the line.
I have found that the spools of solder are usually to be found at car boot sales, sometimes for pence, The green tail rubbers are cheap as chips on a certain auction site .
OMR
Hurrumph....... whatever happened to Handlines ?