I admit that with large amount of extra long trains it is just more efficient to go two line track. But for factory designed just to launch a rocket I do not see a need for something larger 1+2 trains. Acutally design above supposed to support these trains, but I've measured them vertically. Silly ...

Won't we be obligated to do such things when more space stuff is added to the game ?

In my one way rail network I use "buffers" for intersections:
https://imgur.com/gallery/H53oy9u
So I do not see how roundabout is "better". Not saying it is worse, but that would be nice to see your design without extra fiddling with mods and strings.

Now with chain signals, making a simple diamond intersection is straightforward enough for single rail applications.
Diamond.png

I have found an effective way to use single rail with passing sidings on maps where stone supply is initially a problem, as was mine. Chain signals were instrumental ...