I still use a modified GI LBV.
This is my "PLA parachutes in the sky"(SHTF) rig,I like to train with it occasionally,but mostly use a low profile rig.
I got posts of my mods at geardo.com forums and would be happy to answer questions here about them.
I have a lightweight and heavy setup.The lightweight setup is a shorty (sheet plastic) ALICE frame with a med bag.I can wear this with my buttpack mounted on the LBV.
I have tried to lose the buttpack for a long time,it boils down to more of a weight than bulk issue(my BP is @ 20 lbs. loaded....lots of lead and metal and 4 qts.h2O).I just adapted my rig with fastex and straps that hang the buttpack that are independent of the lbv straps.I setup my belt with fastex hangers so I can move my buttpack to either side for readier access(hangs over protectve mask on leg).
I also carry a CFP style assault pack on top of the alice with a 'sustainment load' and plenty of empty space to quickly stash things.
If I drop the alice frame,I still have my buttpack,and if I 'need' shelter or sustainment,I grab the CFP assaultpack.
My heavy rig is a modified(old school)Jansport frame.On the frame I hook the med. Alice rig on top,a partially loaded cfp-90 under,and wear my buttpack fastexed to the frame.
I've used this heavy setup while 'prospecting' being able to split my loads and stash units without alot of re-packing.
My battle rig/packs are worn over armor,with my pack worn over LBV.I know what you mean about poorfitting ruck straps,if I need padding it will be the armor(enhanced with sorbothane pads) that supplies it,and I built straps with removable padding for both my lbv and ruckstraps to make wearing that stuff more comfortable for me.
Padding is important,the shoulders can take a worse beating than the feet from a heavy load,but at the distance the pack straps are from skin and muscle with a combat load,pack straps become more of a weight distribution tool than shock absorbing,IMO.
I set up(modded) a BHI eod vest as a tac-medic rig, now worn without a belt,I've used it under a pack alot and the mesh is most comfortable.With a pistolbelt mounted it can carry quite a load.
I've been spending my gear money on armor,trying to make my old shooting gear work.So far`I've been able to adapt what I have and set it up so I can train,and will gradually upgrade my rig piece by piece,starting with a holster.
Bulletcatchr