Custom/Additional deck options

Is your feature request related to a problem? Please describe.
I’m maintaining a few chinese textbook decks (My anki decks for learning chinese) that use hanzi writer (hanziwriter.org/) for quizzes. I have the problem that right now it is quite awkward to make e.g. the size of the quizzes configurable.

Describe the solution you’d like
I think the best solution would be to allow decks to have custom options presets with defaults and type constraints, e.g. adding to dconf an option “custom” that can include entries such as

"quizSize": {
  "default": 200,
  "doc": "Size of hanziwriter quizes",
  "type": "number"
}

The templates should then be able to read out those options by e.g. {{CustomOption:quizSize}}.

Describe alternatives you’ve considered

  1. Using tags to encode configuration
    • Advantages: Configurable by card.
    • Disadvantages: No clear documentation of the available keys & values, higher technical barrier.
  2. Using _ media files for configuration.
    • This is my current approach.
    • Advantage: One single file.
    • Disadvantage: High technical barrier to find config file and change it., Not possible to properly upload on ankiweb due to limitation uploading _ files.