font-family rules should be quite limited in usage.

Typically most designers recommend no more than three fonts to be used in an application.

Given that font-family rules typically have fail over settings it makes sense to only have a few of these rules declared within a single application or website. Then we have consistency.

So for Iguana X it probably makes sense to define the main font family for the application and just override it in a few special areas like the translator which needs to have fixed width font.