Hollow adjustable semi circles! (Well, more like semi fuselages! XD)
You’d be able to adjust height, width, and length, similarly to how fuselage blocks are adjusted. And the thickness of the outside adjusted in a similar way to how you can adjust the thickness of an inlet, except you can adjust the thickness of both the front and the back. 100% would be closed, 5% would be minimum thickness. Oh and you can also change the corner types too. XD
Could be used to make egg shaped fuselages, make writing, building dash boards, and minor details.
That would be amazing.