Despite the inherent inefficiencies of doing so, I would like to destroy/raze/unbuild enemy cities as I overtake them. Typically, the reason I would prefer to do this is to determine for myself where exactly my cities are located and their relative position to one another. Overtaking an enemy faction's city puts it under my control, of course, but is there any way other than slowly starving out or colony-pod-population-diving a city? Perhaps some way to raze it to the ground, maybe even scoring resources from the process?

You need an active military unit stationed in the city.
In the contextual menu (right-click), select "Action…" > "Obliterate Base" or press Shift + B.

The base destruction is instantaneous and grant you no resources, and is seen as an atrocity by the other faction leaders.

Excellent, thank you. Looks like an atrocity I'm finally willing to consider.

If you're capturing enemy cities, you might as well finish the game off than throw away established production.

Another way is (at least for small bases) to build colony pods while having no workers generate any food. Each pod costs one population. If the base has only one population left you will be asked if you want to abbandon it in favor of a colony pod.