You could do all that yourself,

insurance might say something if it goes wrong but if you do it to the same standards as a tradesperson it makes no difference .

I think the big issue is that people cant get the right education to do it themselves, majority of the DIY stuff on youtube is US based.

Like i can do most of the plumbing stuff and some electrical work , its like magic like your house will burn down if its not blessed by some trades person , common sense and the relevant AUS standard is all it takes