In 2016, I posted up some slides from a Doug Church talk about Object Systems (with examples from Thief) from around 2003 or so.
I've now found another good talk called "Building Object Systems" by Alex Duran from GDC 2003, who worked at Looking Glass and Ion Storm, working on the Thief and Deus Ex games.
The talk is focussed on his experience writing the object system for Thief 3 and Deus Ex 2, and it is largely based on the earlier Thief Object System (work done by people such as Marc LeBlanc and Doug Church).
The AUDIO can be found here on the GDC Vault. I would definitely recommend listening to that.
The SLIDES that accompany the talk can be found here.
I found it hard to find the slides for the talk, so I thought I'd share them here as an easier way for anyone else to find them.