Read-Only access to non-custom GUI ...please?

[AenAllAin]

Would it be possible to get just read-only access to the standard GUI elements like the crafting menu, the mini-map, or whatever; and their meta/supporting elements (i.e. GUI styles)?

EDIT: I finally found the "slot_button_style" under core; so that takes care of the GUI Styles use-case mostly.

I just want to make a custom GUI element that re-uses some of the default GUIs components (like container tables, and item slot frames), so that it fits in with the game and doesn't look hackish. Right now all I can do is guestimate how to make pieces that match the default UI. ...and doing it that way is immediately broken if Factorio ever implements UI skins.

Also, just to pile on, is their any possible way to mod or customize entity GUI Elements? For instance, the container GUI for a custom container prototype/entity; can I add some of my own GUI elements to my own custom prototypes, or even override the default GUI for entities that have them? For example, I'm writing a container mod which has two inventories, and I would like to show both of them simultaneously in their own section of the container GUI whenever you open one of these containers.