yeah I would always use a lighter line for the sinker but not so light that a slight abrasion would leave my sinker behind.
The idea of the bottom live bait rig is to try keep the baitfish at a certain depth.I would use this rig mainly for john dory and I would prefer to keep the baitfish around about 2ft off the bottom without too much freedom, hence the shorter hook trace.
By using a snap swivel and letting the baitfish cover the whole water column is a good idea if you are not really trying to target a certain species but if adding weight or adding a float you would have to be pretty precise as to how much weight/bouyancy you add because as the baitfish gets tired or nears death its either going to sink to the bottom or float to the surface.Even without the added weight etc its prob going to do the same thing especially if theres a strong current.
A balloon rig would prob be alot better for covering different depths.Provided you have a rough idea of the depth you are fishing then you can adjust the length of the main trace to suit.Obviously you wouldnt want it too long or landing a good kingi or something would be difficult.I mean it would be a pain in the ass to have the swival hit the first eye of the rod only to still have 5 or 6metres of trace you have to pull in by hand with a 15 kilo kingi going nato on it mind you it would be exciting
I should of really mentioned that the bottom rig I would use would be primarily used for targeting snapper and John Dory with live bait.Which reminds me…I must try it out over the holidays