Due to how presets are made, the "construction > big" preset crashes the save with the following error: https://imgur.com/a/ZO4eIQx.

This is most likely because K2 change the sprite of the fission reactor

Ill check the issue

After testing, it is not K2 that is the problem, but the fact that Space Age is not active.

Also, the GUI is shown every time the mod list is changed, making it a little too OP

the gui will not give you the item again (should not at least).
I never changed the name of the window but the gui is needed because if you cahnges the mod list you might want to change the quickstart.