Doom gameplay is built around a simple user interface that uses few keys and can easily map to controller. A minimal control set requires four directional keys plus 8 action keys.
This setup leaves much to be desired, but provides access to every control and meta-control needed to play the game and can map to something as simple as a Super Famicom controller.
Most source ports provide the user with a way to map each action to any control available, but generalizing the controls should allow for a developer to change what the actions do.
In a typical kart-racing game, keys for "strafe" and "run" are unnecessary, and only one item is held at a time. In such a case, three of the action buttons can be replaced. The player needs an "accelerator" key and a "brakes" key. The "fire" key can still activate the currently held item. Other keys can be repurposed to activate a horn, a rear-view camera, a "drift", or a "hop". This example requires the controls can be modified to adjust the player object's physics; a non-trivial proposition, but perhaps worth it to generalize the engine in a subtle way.