I did something like this a bit ago, just for some shiggles & because I dig the old school belt systems, but always wanted something a bit more up to date than surplus stuff that is 30 plus years old. What I came up with is this:
Gear list is this:
ATS padded war belt: You could go with the HSGI, but it costs more & the rubber seems like it would be a heat sink.
HSGI modular padded shoulder harness: I had no idea hsgi made these but they are perfect for this kind of setup.
SKD PIG sternum strap: this is another piece of semi hidden gear I don't think a lot know about or think about, it really helps keep the whole setup situated & centered.
Thats the bones of the system, from there you can add whatever pouches you like since its molle. I have some SOE gear Rallyman pouches for mags, though TT universals work well too. ATS roll up dump pouch, SOE gear buttpack, some surplus multicam canteen pouches because they are the easiest to place canteens back in, one handed. I had some Eagle canteen pouches & the elastic made it a total PITA to put a canteen back with one hand. ATS med pouch & thats about it. Easy to reconfigure, no metal clips digging into you & best of all, no slavshit, friends don't let friends buy slavshit