Imagine an element with the properties of both TTAN and WAX. This idea has just that and more.
Element: Metallic glass (or MGLS)
Like TTAN, MGLS conducts electricity, blocks all pressure, and doesn't heat up as it conducts electricity. But unlike TTAN, MGLS is acid proof and blocks pressure, even when sparked (TTAN let's pressure pass when sparked.) It melts into lava at just 500C (the lowest melting point of any element that melts into lava.) Unlike other kinds of LAVA, molten MGLS has the same viscosity of MWAX; meaning, it falls at the same same speed, thus reducing lag. And like MWAX, molten MGLS solidifies almost instantly; whereas, other kinds of LAVA can take up to a whole second to solidify. MGLS can be made by rapidly cooling molten IRON, just as RIME can be made by rapidly cooling WTRV.
NOTE: For those of you who haven't noticed, LAVA normally falls slower than MWAX. But if LAVA had a ctype of MGLS, it would fall at the same speed.
"LAVA" saves can get laggy, given LAVA's viscosity. If it has the viscosity of MWAX, it could be useful in building "metal object" factories that move faster due to a higher FPS. And having such a low melting point means that molten MGLS can be contained by solids that would normally melt into LAVA themselves, such as METL, IRON, or even BRCK. It would also give IRON another use, as IRON is only really useful in 2 ways: METL factories, and electrolysis (making IRON rust isn't the only way to make BRMT.) The possibilities of MGLS are limitless.
I'm talking about uses unique to IRON. There are only 2 of those, and MGLS would make a third one.
EDIT: If no one finds this interesting, I have another idea. MGLS could also allow photons to pass through.