This incredible thing in pic 1 is the first approved design for Parliament house in Melbourne, from 1855 – when Victoria only had 200,000 people. It was designed by Peter Kerr and John Knight, who oversaw the building of the chambers and library 1856–1860, then nothing happened for 18 years. In 1879 Peter Kerr alone redesigned the front and tower, much simpler and grander (and a bit narrower without the side column screens). It’s often said our Parliament House was inspired by Leeds Town Hall, designed 1853, completed 1858, but clearly the 1855 design wasn’t, except perhaps the general idea and the tower, but the new design perhaps was – albeit bigger and more elaborate, and with a dome that’s more Baroque than Neoclassical. And yes why not build the dome, you could do it in steel frame and stone veneer or artificial stone (which looks fine imho), and also complete the two side wings while you’re at it.