Each Historic Preservation Zone dates to a different period and has a distinct style or styles. The city has published design standards for each. The historic period fro Armory Park is 1860s to 1945. Below are links to guidelines and standards to help design a suitable project.
Tucson has general standards which are applicable to all HPZs (Armory Park specific guidelines are at paragraph 7.2):
Updated Armory Park Design Guidelines are now in a lengthy review process. Here is the link to the files related to the draft Design Guidelines updates: https://drive.google.com/open?id=1Sgbt64-YA6t99Hj2fcuqQ3Awdvh9iMG1.
The latest version is here: https://drive.google.com/file/d/1Q1eCbYrOmTG__XeeXx1tWx8iWj7J4KSt/view?usp=sharing