The KTW round was made using tungsten . . . It was made to pierce soft body armour.
No, it wasn't. It was made to pentrate things like car bodies and such. When first introduced circa 1970, soft body armor was very uncommon. (When did Second Chance first start using Kevlar to make vests?)
How about Mercury-cored lead/copper jacket hollow points?
I remember seeing "Mer-Core" bullets as reloading components at a gun shop outside Chicago around 30 years ago. neither my father nor I wanted anything to do with them, as we both knew mercury was toxic.
My idea . . . how about a hollowpoint with a bunch of tungsten rods inside, held together with a conventional copper jacket. The rods would be sort of like captive "flechettes" and longer on the edges, shorter towards the bullet axis, to form the hollowpoint. You could fill the spaces between the rods with something like potassium metal, and put a Teflon ball up front, to make it sort of like Pow-R-Ball ammo. On impact, the tungsten rods would tumble and scatter, aided by the violent exothermic reaction of the potassium.
On a more down-to-earth level, I'd like to see a commercial HBWC seated backwards, in .38 +P or .357, to give today's little J-frame snubbies more punch. The original Hydra-Shok Scorpion ammo was based on this concept (though they added the famous post) but the loading offered was disappointingly anemic.