Definitely a worthy addition to the game, the doors to get here were in the original level and there was a "Library Map Note" present in dialog.tlk as well.
I have already adapted it, the modders resource version contains an empty module, but the installer version can install it directly to the first game, someone just needs to add some content to them, I know there is already one modder working on it.
I did consider fixing the arch, however there was no rubble present from it so I figured perhaps it had been damaged a long time ago, rather than recently.