Hi!
I think everyone who worked a lot with native Unity GUI API have written his own framework (shell) under it.
Is it true or may by you didn’t?
If you was writing your own framework for native unity GUI (to do work more more faster), have you already shared it for forum users?
I think, yes.
Native Unity GUI is not enought comfortable and you are obleged to extend it with your own littte framework.
UPD:
You can see a lot of shared GUI tools at Scripting/GUI https://www.assetstore.unity3d.com/#/category/111 or Editor Extensions/GUI https://www.assetstore.unity3d.com/#/category/141 categories of Asset Store
eDriven.Gui is (currently) based on IMGUI: http://edrivengui.com/