Griz:
Regarding the tungsten-core bullets being 'heavier-for-calibre' while still remaining the correct length for the barrel's twist rate:

At the same chamber-pressure, they will be slower, so will need a faster twist rate anyway to achieve the same rpm in flight for stabilization.

Law of diminishing returns. Option No.1 is looking better all the time!

Remember that the cartridge developers a century ago went through all this prior to release, especially the Brit NE designers, and they already chose the heaviest practical bullet at the desired velocity, for each cartridge. Sure, we have a few new bullet materials that weren't available then, so it's worth revisiting for sure, but as others have pointed out, a heavier bullet at lower velocity is probably already available in another cartridge's factory load!