Johann David Steingruber (1702-1787) was an architect in what is now Germany. In 1773, he published this alphabet book which used letters as outlines for building shapes. Although some letters, such as T, turn into buildings very easily, others, such as P, R, and Z, look delightfully eccentric.
A more fanciful architectural alphabet from 1753 can be found here. Perhaps the two approaches could be combined into single buildings.