Hello, longtime Android WatchMaker Premium user, new iOS WatchMaker Premium user here.
When editing a Text component, please include all of the iOS system installed fonts in the Font selection list (not just the ones that you built into the application). This would allow users to install custom fonts onto the device, and then use them in watch faces.
Here is an example of Objective C code to get an alphabetically sorted list of system installed fonts:
NSArray *fonts = [[NSMutableArray alloc] init];
NSArray *fontNames = UIFont.familyNames;
NSArray *fontNamesSorted = [fontNames sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)];
[fonts addObjectsFromArray:fontNamesSorted];
To install a custom font onto your iOS device, you can either use an app like AnyFont ($1.99), or it's very easy to create a .mobileconfig file using the Apple Configurator 2 (free in the Mac App Store). Simply open up Apple Configurator 2, create a New Profile, fill in the General tab fields, scroll down to Fonts on the left side, and drag your .ttf into the window. Save your profile and email it to yourself. Open the attachment on your iOS device to install the profile and your custom font is now in the OS font library, and will show up in the UIFont.familyNames list.